Yesterday Google announced their Javascript Closure Library is available for public use. You may think you need another Javascript toolkit like you need another browser, but this library offers the experience of the Google collective which means speed, stability and cross browser support.
It also means we now have access to the libraries used to implement all the nutty things Google does in their most popular apps. Take this toolbar for example, used in Gmail and Google Docs, now available for you to do even cooler things with.
They also provide even higher level functionality, like this rich text editor used in Gmail and Google Docs which makes use of the toolbar shown above.
The library also includes a vast number of complex (and possibly obscure) JavaScript elements you would never want to code yourself, like this two thumb slider.
OK, I know what you're saying, there are already lots of JavaScript widgets like this at scriptkiddies.com and icantcodemywayoutofajsbag.net, but the key difference is this library has been battle tested in Gmail, Google Docs and Google Maps.
This is industrial strength stuff that will run fast, and is organized in a way that minimizes the amount of JavaScript you need to attach to each page. This reduces both the size of the scripts that need to be downloaded and the time the browser takes to evaluate them.
Want to see more? Browse over 70 demos on the Closure Library documentation page (click the demo tab). Ready to ditch the pickup and gas up the earth mover? Hop on over to the getting started pages.