Evaluating CSS3 & HTML 5 features
When Can I Use... is a fantastic site to use when you need to decide whether or not to use some of the new CSS3 and HTML5 hotness. It offers comprehensive compatibility tables for relevant versions of all browsers, mobile and immobile, and even links to workarounds so you can just squeak by on using that one feature you just have to have. I'm planning on redesigning this site soon, and It's going to be a big help. Also, IE users, things here will still be readable after that, but otherwise, you're on you own until IE9 is ready for primetime.