Learning the Fretboard
This is a timed flashcard tool to help you to learn the notes of a fretboard. I have no idea whether it actually helps you to learn the fretboard, but you're either here because it might, or because you just want to play around with it.
At the moment, there is very little configuration to this. Just change the tuning to a comma-separated list of notes in the URL. If you need sharps and flats, you will have to use my standard because I couldn't find an established one. Sharps and flats are notated alphabetically, so D♯ would be written "dseb" which stands for D Sharp E Flat. A♯ would be "asbb". So standard tuning down a half step becomes dseb,gsab,csdb,fsgb,asbb,dseb. It's a bit of a pain but it's cleaner than having to URL encode UTF-8 characters.
This should also work for bass and ukulele (of course ukulele has two) tunings as well as guitar, unless there's something weird going on there that I don't know about.