Where to get good free images

Choosing a new desktop background? Need pictures for a report? Just want beautiful photos? I've got 2 words: Wikimedia Commons.

Their "Featured Pictures" category contain some of the best images on the web, and they're all free. As part of the Wikimedia Foundation (of which Wikipedia is part), 99.99% of the images in Commons are open source. And if you think "free" means "low quality", here are some examples.

And of course, the best:

Just click for higher resolutions (although Blogger seems to downgrade them quite a bit). I'm currently using the second one as my desktop, and it works for 1920 by 1200 resolution perfectly. For more, check out Wikimedia Commons Featured Pictures.