I’d like to mention iconfinder.net. They’re a great site with a ton of free icons. You can even use some commercially without links back to the site for credit. The icons are not cheap looking either. There are high quality icons and some really unique styles as well. They have a great search and you can filter by size/licence. I get icons there all the time. Now if someone had free commercially usable stock photography, I’d be all set!
If you have any icon/image sites you use to find commercially usable images, I’d love to hear about them in the comments!