A few handy apps for your toolbelt

I've run across several online tools recently that have been quite useful for things like quick prototyping and proof-of-concepts. Enjoy:

JavaScript Tools

jsconsole.com - great if you need to play with some JavaScript and don't want to bother cracking open FireBug or dev tools. Does some basic auto-completion, as well.

JS Bin - for more comprehensive testing. Also allows you to save your work and share with others, who can then fork your initial code.

jsFiddle - similar to JS Bin, only with a few more bells and whistles, including the ability to test AJAX requests.

jsPerf - a tool specifically for testing JS performance. Be sure to scroll all the way down and hit "Browse". Chances are someone may have already thought of what you're hoping to test.

CSS Tools

CSSDesk - similar to JS Bin or jsFiddle, only built specifically for CSS.

CSS3 Generator - a playground for many of the new CSS3 properties.

CSS3 Please! - another, somewhat more colorful, CSS playground.

CSS Border Radius - does one thing, and does it well: generates cross-browser border-radius styles slightly more quickly than you could type them out.

If you know of a similar tool, please add it in the comments!