I found/made some useful GreaseMonkey scripts and didn't know where to post them. I figure they're technical enough.
phpbb3:
Quick Reply: http://userscripts.org/scripts/show/10948
Quick Edit: http://userscripts.org/scripts/show/11064
Hover Preview: http://userscripts.org/scripts/show/22852
NationStates:
Remove Rounded Borders: http://userscripts.org/scripts/show/51053 (updated!)
If you find any other useful scripts, share them!