A List Apart has an interesting overview of CSS3 animation and user experience . I have seen a few of these effects around, and they really add to the user experience while being pretty light.
An interesting way to get background gradient animation with CSS3 – basically by using a larger background image and moving the position on hover. Check out the original article .
Some very nice effects with sources listed in this article . My favorites (with direct links and images): – black and white images (might try these for STGThumb albums) – page top shadow (looks very nice)(broken link) – stitched effect – corner ribbon
Very interesting post at WebDeveloperJuice showing 8 just arrived magic effects of css3 worth to know . It is hard to choose a favorite, but the paper fold looks very nice. Update: a few more effects on More Cool CSS3 Effects