Userscripts.org

This script adds new links under the user screen name to help you search for the screen name on Twitter (@screenname, #screenname, and others). See Screenshot.

Facebook Chat Cleaner userscript hides all offline users and the Ticker in Facebook chat. Plus, it also hides Facebook ads on new Timeline profile and Ticker visible on Facebook homepage.

Facebook auto login for shared computer, adds a "Who?" drop down list and logs in the selected user, useful for husband/wife or others that share a computer and don't mind if their spouse/others knows their password

Returns the average level of the current chat room and the people who are lvl 40 or better with the command: /media

Adds a link to user pages to search for their comments via Google

BETA v0.5: script to plonk specific users on every adobe forums page (new jive clearspace based forums)

Lets you add tags to any flickr user, you can then view the tagged users via a whole range of different filters, including view by tag, view tagged users photos,favourites,testimonials,most interesting photos, photos of that user etc, etc

Get all the users that have multiple posts on a thread and show the number of posts