Desde la versión 9.50 de Opera se eliminaron las extensiones de los ficheros de la caché, cosa que dificulta enormemente la búsqueda de cosas en la caché.

Es posible añadir a opera:cache vistas en miniatura, búsqueda y ordenar por nombre de archivo y  tamaño, para facilitar la navegación por la caché.

La manera de hacerlo es la siguiente:

1. Copia el fichero de idioma (*.lng) que utilices (normalmente se encuentra en la carpeta locale, en el directorio de instalación de Opera).
2. Abre el fichero de idioma con un editor de texto y reemplaza la línea -1713924769 por esto:

-1713924769="Size<script type='text/javascript'>function sorter(t){var table=document.getElementsByTagName('table')[0];var node;var col=t.cellIndex;var span=t.getElementsByTagName('span')[0];var a=new Array();var tbody=table.getElementsByTagName('tbody')[0];var tr=tbody.getElementsByTagName('tr');for(var i=0;(node=tr[i+1]);i++){a[i]=new Array();a[i][0]=getConcatenedTextContent(node.getElementsByTagName('td')[col]);a[i][1]=node}a.sort(_sort);var dtitle=span.getAttribute('title');if(dtitle==0){a.reverse()}dtitle=dtitle==0?1:0;span.innerHTML=dtitle==0?'↓':'↑';span.setAttribute('title',dtitle);for(var i=0;i<a.length;i++){tbody.appendChild(a[i][1])}function _sort(a,b){var a=a[0];var b=b[0];if(Number(a)&&Number(b)){return sort_numbers(a,b)}else{return sort_sensitive(a,b)}};function sort_numbers(a,b){return a-b};function sort_sensitive(a,b){if(a<b)return-1;if(a>b)return 1;return 0};function getConcatenedTextContent(node){var _result='';if(node==null){return _result}var childrens=node.childNodes;var i=0;while(i<childrens.length){var child=childrens[i];switch(child.nodeType){case 1:case 5:_result+=getConcatenedTextContent(child);break;case 3:case 2:case 4:_result+=child.nodeValue;break;case 6:case 7:case 8:case 9:case 10:case 11:case 12:break}i++}return _result}};document.addEventListener('load',function(){for(var i=0;document.links[i];i++){document.links[i].target='_blank'};var tr=document.getElementsByTagName('tr');var sf=document.createElement('input');sf.type='text';sf.defaultValue='Search';sf.style='font-size:100%;margin:0 20px 0 30px;width:40%;';sf.addEventListener('focus',function(){if(this.value==this.defaultValue){this.value=''}},false);sf.addEventListener('blur',function(){if(!this.value){this.value=this.defaultValue}},false);sf.addEventListener('keyup',function(){var v=this.value.toLowerCase();for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild.innerText;if(p&&p.toLowerCase().indexOf(v)==-1){l.style='display: none'}else{l.style='display:table-row'}}},false);var bt=document.createElement('input');bt.type='button';bt.value='Thumbnails';bt.style='font-size:100%;cursor:pointer;float:right;';bt.addEventListener('click',function(){var b=/\.(jpe?g|bmp|gif|png|ico|swf|flv)$/i;var f=/\.(swf|flv)$/i;for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild;var c=l.lastChild.firstChild.innerText;if(l.offsetHeight!=0&&p.childNodes.length<2){if(b.test(c)){var stl='float:right;border:1px dotted black;margin:1px;padding:1px;max-height:100px;max-width:100px;';if(f.test(c)){var dv=document.createElement('div');p.appendChild(dv);dv.innerHTML='<EMBED src='+p.href+'>';var fh=dv.firstChild;fh.setAttribute('height',100);fh.setAttribute('width',100);fh.setAttribute('style',stl+'content:normal;display:inherit;outline:none;background-image:none;')}else{var image=document.createElement('img');image.setAttribute('src',p.href);image.setAttribute('style',stl);p.appendChild(image)}}}}},false);var th=document.getElementsByTagName('th');th[2].appendChild(bt);th[2].appendChild(sf);var addSort=function(ele){var span=document.createElement('span');span.title='0';span.appendChild(document.createTextNode('•'));ele.insertBefore(span,ele.firstChild);ele.onclick="sorter(this);";ele.style.cursor='pointer';};addSort(th[0]);addSort(th[1]);},false)</script>"

Si tienes la última Opera 9.51, copia lo siguiente, que es una versión optimizada del código:

-1713924769="Size<script type='text/javascript'>function sorter(t){var _sort=function(a,b){var a=a[1];var b=b[1];if(Number(a)&&Number(b)){return a-b}else{if(a<b)return-1;if(a>b)return 1;return 0}};var col=t.cellIndex;var span=t.selectSingleNode('span');var tbody=document.selectSingleNode('//tbody');var tr=tbody.selectNodes('tr[td]');var len=tr.length;var a=new Array(len);for(var i=0;i<len;i++){a[i]=new Array(2);a[i][0]=tr[i];a[i][1]=a[i][0].selectNodes('td')[col].innerText};a.sort(_sort);var dtitle=span.getAttribute('title');if(dtitle==0){a.reverse()};dtitle=dtitle==0?1:0;span.innerHTML=dtitle==0?'↓':'↑';span.setAttribute('title',dtitle);for(var i=0;i<len;i++){tbody.appendChild(a[i][0])}};document.addEventListener('load',function(){for(var i=0;document.links[i];i++){document.links[i].target='_blank'};var tr=document.getElementsByTagName('tr');var sf=document.createElement('input');sf.type='text';sf.defaultValue='Search';sf.style='font-size:100%;margin:0 20px 0 30px;width:40%;';sf.addEventListener('focus',function(){if(this.value==this.defaultValue){this.value=''}},false);sf.addEventListener('blur',function(){if(!this.value){this.value=this.defaultValue}},false);sf.addEventListener('keyup',function(){var v=this.value.toLowerCase();for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild.innerText;if(p&&p.toLowerCase().indexOf(v)==-1){l.style='display: none'}else{l.style='display:table-row'}}},false);var bt=document.createElement('input');bt.type='button';bt.value='Thumbnails';bt.style='font-size:100%;cursor:pointer;float:right;';bt.addEventListener('click',function(){var b=/\.(jpe?g|bmp|gif|png|ico|swf|flv)$/i;var f=/\.(swf|flv)$/i;for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild;var c=l.lastChild.firstChild.innerText;if(l.offsetHeight!=0&&p.childNodes.length<2){if(b.test(c)){var stl='float:right;border:1px dotted black;margin:1px;padding:1px;max-height:100px;max-width:100px;';if(f.test(c)){var dv=document.createElement('div');p.appendChild(dv);dv.innerHTML='<EMBED src='+p.href+'>';var fh=dv.firstChild;fh.setAttribute('height',100);fh.setAttribute('width',100);fh.setAttribute('style',stl+'content:normal;display:inherit;outline:none;background-image:none;')}else{var image=document.createElement('img');image.setAttribute('src',p.href);image.setAttribute('style',stl);p.appendChild(image)}}}}},false);var th=document.getElementsByTagName('th');th[2].appendChild(bt);th[2].appendChild(sf);var addSort=function(ele){var span=document.createElement('span');span.title='0';span.appendChild(document.createTextNode('•'));ele.insertBefore(span,ele.firstChild);ele.onclick="sorter(this);";ele.style.cursor='pointer';};addSort(th[0]);addSort(th[1]);},false)</script>"

Puedes descargar el fichero modificado en español de España: es-ES.lng

3. Accede a Herramientas, Opciones, General, Detalles, Idioma de la interfaz de usuario, Seleccionar y escoge el fichero que acabas de modificar.
4. Reinicia Opera.
5. Accede a opera:cache y comprueba las nuevas funciones.

AVISO: al acceder a opera:cache y utilizar estas mejoras puede ralentizarse mucho el ordenador.

Actualización: Para Opera 10 el código es:

-1713924769="Size:   <script type='text/javascript'>function sorter(span){var _sort=function(a,b){var a=a[1];var b=b[1];if(Number(a)&&Number(b)){return a-b}else{if(a<b)return-1;if(a>b)return 1;return 0}};var dir=span.innerHTML.charAt(0);var col=span.parentNode.cellIndex;var tbody=document.selectSingleNode('//tbody');var tr=tbody.selectNodes('tr[td]');var len=tr.length;var a=new Array(len);for(var i=0;i<len;i++){a[i]=new Array(2);a[i][0]=tr[i];a[i][1]=a[i][0].selectNodes('td')[col].innerText};a.sort(_sort);if(dir!='↓'&&dir!='↑')dir=arguments[1]?'↓':'↑';if(dir=='↑'){a.reverse()};span.innerHTML=(dir=='↑'?'↓':'↑')+span.innerHTML.substr(1);for(var i=0;i<len;i++){tbody.appendChild(a[i][0])}};if(location.search)document.documentElement.style.display='none';var style=document.createElement('style');style.setAttribute('type','text/css');style.appendChild(document.createTextNode('td{border-width:1px 0;border-style:solid;border-color:#DEDEDE #F5F5F5 #F5F5F5;}td:first-child,td:first-child+td{border-width: 1px 1px 1px 0;border-color:#DEDEDE #DEDEDE #F5F5F5 #F5F5F5;}th{width:auto;}td+td+td a{-o-text-overflow:ellipsis;overflow:hidden;display:block;}'));document.getElementsByTagName('head')[0].appendChild(style);document.addEventListener('load',function(){for(var i=0;document.links[i];i++){document.links[i].target='_blank'};var tr=document.selectNodes('//tr[td]');if(location.search){var ls=location.search.substring(1);if(ls)for(var i=tr.length-1,ti;ti=tr[i];i--){var tt=ti.lastChild.firstChild.innerText;if(tt&&tt.indexOf(ls)==-1){ti.parentNode.removeChild(ti)}};document.documentElement.style.display='block'};var sf=document.createElement('input');sf.type='text';sf.defaultValue='Filter';sf.style='font-size:100%;margin:0 20px 0 30px;width:40%;';sf.addEventListener('focus',function(){if(this.value==this.defaultValue){this.value=''}},false);sf.addEventListener('blur',function(){if(!this.value){this.value=this.defaultValue}},false);sf.addEventListener('keyup',function(){var v=this.value.toLowerCase();for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild.innerText;if(p&&p.toLowerCase().indexOf(v)==-1){l.style='display: none'}else{l.style='display:table-row'}}},false);var bt=document.createElement('input');bt.type='button';bt.value='Thumbnails';bt.style='font-size:100%;cursor:pointer;float:right;';bt.addEventListener('click',function(){var b=/\\.(jpe?g|bmp|gif|png|ico|swf|flv)$/i;var f=/\\.(swf|flv)$/i;var stl='float:right;border:1px dotted black;margin:1px;padding:1px;max-height:100px;max-width:100px;';for(var i=0,l;l=tr[i];i++){var p=l.lastChild.firstChild;var c=l.lastChild.firstChild.innerText;if(l.offsetHeight!=0&&p.childNodes.length<2){if(b.test(c)){if(f.test(c)){var dv=document.createElement('div');p.appendChild(dv);dv.innerHTML='<EMBED src='+p.href+'>';var fh=dv.firstChild;fh.setAttribute('height',100);fh.setAttribute('width',100);fh.setAttribute('style',stl+'content:normal;display:inherit;outline:none;background-image:none;')}else{var image=document.createElement('img');image.setAttribute('src',p.href);image.setAttribute('style',stl);p.appendChild(image)}}}}},false);var th=document.selectNodes('//th');th[2].appendChild(bt);th[2].appendChild(sf);var addSort=function(ele){var arg=arguments[1];var txt=ele.firstChild;var span=document.createElement('span');span.title='Sort';span.appendChild(document.createTextNode('•'));ele.insertBefore(span,txt);span.addEventListener('click',function(){sorter(this,arg);for(var i=0;i<th.length;i++){var s=th[i].firstChild;if(s!=this)s.innerHTML='•'+s.innerHTML.substr(1)}},false);span.style.cursor='pointer';span.appendChild(txt)};addSort(th[0]);addSort(th[1]);addSort(th[2],true);if(location.search)sorter(th[0].firstChild)},false)</script>"

Fuente