By far my favorite mouse killer is the Ion window manager (http://modeemi.fi/~tuomov/ion/).

Using the lua config I changed a bunch of the key bindings so that the entire environment behaves like vim. I can easily change windows using the vim directional keys, which are second nature by now. I never lose windows behind other windows.

After a few days in this environment you start looking for apps that provide a keyboard interface to all their functionality so you can throw away your mouse entirely.

Vimperator is a good example. Also, I use irssi (http://irssi.org/) for all chat and instant messaging. We modeled the chat interface for ShopTalk (http://shoptalkapp.com) after irssi for exactly this reason.