Free download:

Printable CSS 3 Cheat Sheet (PDF), a complete listing of all the properties, selectors types and allowed values in the current CSS 3 specification from the W3C.

Printable HTML 5 Cheat Sheet (PDF) that lists all currently supported tags, their descriptions, their attributes and their support in HTML 4.

Note: HTML 5 won’t be completely supported until 2022, the specification is an ongoing work.

[Thanks to Chris Hanscom from veign.com, via Smashing Magazine]