There are three sites I have run across which have a large amount of graphics available for free download. While searching through google image search can yield decent results, depending on what you’re looking for it can be more trouble than its worth.
Stock.xchng – This is a site for free stock photos. While stock.xchng doesn’t have the largest selection of stock photos, you definitely get more than you pay for. Interestingly enough, stock.xchng is owned by the same folks who own iStockPhoto. You might be wondering why they would offer these images for free, but I think it is good marketing. Alongside the free results, iStockPhoto’s more extensive collection is shown. This probably drives more sales than you would think.
OfficialPSDs – This site is a solution to every graphic designer’s problem. The foregrounds of many images have already been cut out for you and saved as a PSD. This can save you countless hours spent with the lasso tool in PhotoShop. Need some fire graphics for a page you’re designing? A quick search yielded a boatload of results all completely cut out from the background. There are many different types of images on the site, but celebrity images seem to be the most common.
PlanetRenders – This site is very similar to OfficialPSDs. All the images have been cut from the background, except they are saved in PNG format rather than PSD. If you need some cut graphics to design a fan site or convention flyer, this is the spot. There is a wide selection of video games, anime, TV/movie, and fantasy graphics. There’s also quite a lot of fractal renders if you need to add an effect to your background designs.
One thing to keep in mind however with free graphic sites is that sometimes pictures will get uploaded that are not free to use because of copyrights. It is difficult for a site to police all of its submissions, and you should always be careful.