Equipboard is the world's largest database of artists and the music gear they use. It's crowdsourced, so anyone with knowledge (and proof) can contribute to the database.
A music artist's profile contains all the gear they have been spotted using, and conversely a piece of gear can be looked up to see all the artists that use it.
The site also includes extensive lesson and
gear buying guides, including guides to the
best online guitar lessons, and the
best guitar distortion pedals.