ActionScript .5 for Flash Lite 1.1
It’s hard to roll back to the ASpoint5 frame of mind, so this download comes in real handy: grab it from Scott Janousek.

ActionScript 2
I usually work with the code hinting the AS Editor within Flash. Alternatively, SE|PY is quite brilliant to work with, if you’re into 3rd party editors. But the low-tech method of having a tangible AS2 Cheatsheet on hand is always useful. Snag it from ActionScriptCheatSheet.com.

ActionScript 3 (for Flash player 9)

ActionScriptCheatSheet.com also has several great sheets for those of you getting into AS3. There is so much to this new version of ActionScript, that even the cheatsheets are broken down by package.