Firefox extensions

Ad Block
Add Bookmark here
Bookmarks synchronizer
Greasemonkey
Password Maker
Quicknote
Tabbrowser preferences

Undecided on
Bookmarks Synchronizer, Flashgot, Platypus, Tiny url, View Formatted Soure,

Greasemonkey and Password Maker are revolutionary but not well known.
Password Maker provides multiple secure and convenient passwords based on a single "master password".
Greasemonkey makes the customization of web sites easy. By providing a way to execute java scripts aimed at particular websites you can make: Provide a Netflix link next to every movie listed in IMDB; create a text box for adding technorati tags inside the blogger post page, etc.