If you spend a lot of your time looking up all the different methods and functions from your programming language or framework, try gotAPI. gotAPI consolidates a lot of the API documentation scattered across the web and provides a simple live search for it.
Best of all, I can use the same website to lookup Ruby on Rails, Prototype, CakePHP, PHP, and CSS.
Eric
Nice. That could be very handy the next time I need to find some obscure CSS property.