There didn't seem to be many dedicated threads to the Greasemonkey scripts I use for Danbooru and friends, so I'm creating a single thread to mention all of them. As the scripts' pages on Userscripts.org all have their own little forums, specific problems/requests/feedback probably best go there. Firefox runs the scripts through Greasemonkey/Scriptish; Opera and Chrome also support them in some fashion, though I can't offer any help there.
<< EDIT: Moved script list to about:userscripts >>
(And besides scripts, SauceNAO has a Firefox/Chrome extension to help with image searches.)