I've been accumulating greasemonkey scripts for a while, now it's time to release some. I've tested them as much as I can, but if you find any bugs let me know in the comments.
Quake Live Friend Commands
This script adds a few new console commands, the most useful of which is /invite. This allows you to invite someone to your server without leaving the game, and (as it stands) you don't need to add them to your friends list first. Other commands include /addfriend and /clantag (which still needs a /reconnect due to the way QL works).
Quake Live SAM Presets
The new Start a Match interface is awesome, but the only way to save your settings is by pasting them to a text file. This userscript adds local storage of presets, so you can save your favourite presets without losing them, and easily recall them when you want to play them.
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Quake Live Message Beep
If you're like me and leave QL open a lot, maybe you also find you miss messages sent when you're not looking. This script adds a customizable message beep to the Quake Live chat applet. The beep is disabled while you're playing by default, of course.
Quake Live Auto-Config
I wrote this script a while ago with plans to set up different binds for different gametypes and different maps in CTF, but I never got round to it. It did prove useful for automatically disabling r_fastsky on maps with portals though, so here it is. Instructions are in the link.
Finally there's a short Launch in Window Mode
script, if you're like me and don't want to go fullscreen until the game starts.