USO Links - Add's shortcuts links to the login status bar.
Cheezburger AutoPager - Autoloads the next page as you scroll, and uses the arrows to move between posts. Works for the whole Cheezburger network, IPB and vBulletin forums, and some other wordpressish pages
HTTP-to-HTTPS redirector - Replace http:// with https:// in the address bar, to make sure you're using the SSL-encrypted version of a page. Only enable for pages that you know are SSL enabled.