A nice website with good interface. Easy to search and download. Give Almost all kind of icons in all sizes (12px to 128px).
They say “Iconfinder provides high quality icons for webdesigners and developers in an easy and efficient way” .
Nice Icons for every one.
Another good icon search engine with nice interface. Iconlet is simple search engine for free icons, images. For every image user get information about author, image resolution, graphics format and license type. Just type name in search window and you will get a list o available icons, images which you can use in your project.