Lets face it, unless you have a photographic memory, no developer can remember all the different functions, options, tags, etc. that exist. Documentation can be cumbersome at times, thats why I like cheat sheets. They are quick references that feature the most commonly forgotten things on a specific topic. You can print them out and hang them on your wall, or just keep them handy in your bookmarks for quick reference.

I have rounded up over 30 cheatsheets that developers might find useful.

Web Development Cheat Sheets

Databases / SQL Cheat Sheets

Language Cheat Sheets

Version Control Cheat Sheets

Other

Commercially Printed CheatSheets

Visibone - javascript, browsers, colors, fonts, html.

TechnoChallenged - web dev, programming, os, software

Am I missing any good ones? Feel free to post any others in the comments.

Updates: