Greasy Fork

Adds links to the external links sidebar, if the part of the sidebar doesn't exist, it creates it.
Links use the "I'm feeling lucky" equivalent of duckduckgo. So milage may vary, though in my testing it worked pretty well.
If you want to get to the search instead of the mal/anidb page directly you can remove the !duck part from the URLs in the run method.
The way it's set up however makes it really easy to add sites, as long as they are well search engine optimized.

Also, it's tuned only works for anime atm. Manga support may be added in the future.