This is the best breakdown of selectors I've seen. An excellent reference for all Web developers.
html
Close Pixelate
"Inspired by American portrait painter Chuck Close, this script converts an image into a pixelated version using an HTML5 canvas element. It's basically a simple demo for canvas' imageData functionality."
HTML5 Boilerplate
As noted on the site, this is "the professional badass's base HTML/CSS/JS template for a fast, robust and future-proof site" While I likely won't use this whole, there are some very interesting pieces to this worth using, especially in the style sheet and .htaccess files. I'll likely appropriate many of the concepts for my work.
This is an outstanding contribution to the Web development community by Paul Irish and Divya Manian as well as all of the people whose work they built upon.
The HTML5 test
This site provides "an indication of how well your browser supports the upcoming HTML5 standard and related specifications."
html5shiv
I didn't realize Google hosts the HTML 5 Shiv in addition to the other JavaScript frameworks that it's kind enough to provide the community. Nice!
If you want to use HTML 5, the shiv is pretty well a requirement as Internet Explorer (up to and including IE 8) doesn't support the new elements in the spec. Plus it's easy to implement and will only be downloaded by the browsers that need it.
DevCheatSheet.com
Cheat Sheets & Quick Reference Cards for Developers