If you spend any time coding plugins or themes for WordPress, you know the value of a good reference for WordPress API functions. That’s why you should go take a look at QueryPosts right now, and bookmark it. At the time of this writing, you can lookup
all most (for now) functions in the WordPress core, or you can browse by just the new functions introduced in WordPress 3.3 (I’m sure that this will update when version 3.4 comes out, Real Soon Now). A live-search feature makes it easy to identify functions, even if you only know part of the name. Features for inspecting classes or getting information about API hook usage are forthcoming.
Currently, as you browse functions, you get a nice listing of the function names, arguments, return types, description, version of WordPress that introduced the function, and the file that contains it. When you drill into a specific function, you also see the syntax-highlighted source for the function, links to the source on WP Trac and on GitHub, and a list of related functions.
Based on what I see so far, I expect this site to become one of the standard references that WordPress experts rely on.