Greasemonkey
From the projects page you can see I’m pretty keen on Greasemonkey, so I’ll keep this one brief.

The easiest way to get at the scripts here is to use the links to the right, but just to pad this page out a bit, here are some descriptions:
- SA LinkThread Tags – makes the thread tags on SomethingAwful clickable
- Facebook utils – general enhancements to Facebook
- Facebook skin – reskin of Facebook, getting lots of traffic thanks to Google
- Auto refresher – automatically refresh pages at a given interval
- Attached images converter – converts attached images to inline in vBulletin forums
- YouTube trimmer – cuts down the clutter on YouTube video pages, and adds an expand video link
Obviously, having the Greasemonkey addon (or an alternative for other browsers) is a requirement for all these scripts.