documentation
Is Documentation Holding Open Source Back?
A very good, succinct guide to the essential information that a software/technique/project website should contain.
MySQL Cheat Sheet
Every once in a while I can’t use phpMyAdmin for one reason or another, and in that case, it’s very helpful to have a quick, documented list of command line options.
RDoc Documentation
I always seem to have a hard time finding the reference info I need for RoR. This site helps a ton!