I've added short intro sections on vim's command mode, recording macros and a link mentioned by lowks about a Vim cheat sheet.
Mozex - Mozilla Extensions
This is pretty indispensible addon for me. It provides features that should be in Mozilla/Firefox and the author says it as such. What it gives you is a context menu to launch user definable programs for specific actions.
Updated: David Woodhouse, has pointed out that mangling the url, is not a good idea, and one should just pass the mailto: url as is for evolution as shown above