NewsLinksToGoogleGroups converts news:// URLs so they point to Google Groups. (How many of us still have a standalone USENET News client?)
Password Composer is sheer brilliance. You only have to memorize one password for all the web sites you log into, only you can use a different password for each one. How? This script jumbles your password against the site’s domain name in a way that is a bit tricky to unjumble. It’s not military-grade password security, but if you insist on remembering just one simple password, you may as well use this to improve your security.
SkypeLinkify turns phone numbers into Skype links so you can phone someone with a simple click, for about 2.5c/min. Too cool. I’m already a Skype user, but if I weren’t, this convenience might just convince me to start.