Scriptish
Scriptish is the greatest user script engine on the Internet. It was forked from Greasemonkey and made much better.
If you are looking for user scripts, then check out userscripts.org.
News
- 15 Jul 2013 Scriptish Finally Supports @Grant!
- 15 Jul 2013 Improved GM_addStyle and a new @css header
- 15 Jul 2013 Greasemonkey Finally Supports GM_setClipboard!