[http://www.etherpad.com EtherPad] is way cooler than [http://docs.google.com Google Docs] for collaboration. Doesn’t support or require an annoying (for many purposes) WYSIWYG editing mode. Synchronizes with the server instantaneously, as in on every letter you type, not just every minute or even every ten seconds. Loads much faster and feels lighter. Color-codes your text. Built on a server-side Javascript framework called [http://www.appjet.com AppJet], which is the product of a startup formed by a few ex-Googlers.

The only downside is lowered security. EtherPad has no notion of an account, so you’ll have to save the URL to your document yourself (by copying and pasting it somewhere), and it’d theoretically (I would imagine) be possible to brute-force document URLs so as to hunt for interesting things people have typed, and so on.