Userscripts

Tag Health
Tag Health monitors the question quality of a given set of tags on a Stack Exchange site with a sample of about 500 most recent questions.

Close Reason Editor
Close Reason Editor allows you edit the off-topic close reasons which are normally editable only by the site moderators.

Stack Activity
Stack Activity is a simple userscript that shows you the last activity of every question on the homepage, question lists and user pages of any Stack Exchange sites.

##Libraries

instano.js
instano.js allows you to instantly detect if JavaScript is disabled after the page is loaded.

Tools

Frame Rate Distribution
A tool to check the difference in framerates between setInterval and requestAnimationFrame.