Mhh some non-Japanese coverages I can remember so far:
Anamanaguchi, Megadriver, Electro Static Discharge, Game Over, Powerglove, Project X, Repliforce and Stemage.
There also exists numerous (hundreds of) doujin artists from Japan, some that are good or known and I do remember at the moment:
Mintjam (Rock etc), Crow'sclaw (heavy, rock etc.), Aether (Secret of Mana 2 coverages), FMPSG (Coverages with Sega soundchip), Magical Trick Society (Heavy, Rock etc.), S.S.H (Heavy, Rock etc.), ALiCE'S EMOTiON (doujin circle, hardcore, techno etc.), Alstroemeria Records (doujin circle, hardcore, techno etc.), Angelic Quasar (doujin circle, hardcore, techno etc.), C.H.S (doujin circle, mostly t+pazolite's stuff, hardcore, techno etc.), dBu music (doujin circle, heavy rock, techno etc.), IOSYS (doujin circle, random, techno ), SOUND HOLIC (doujin circle, hardcore, techno etc.), TAMUSIC (doujin circle, mostly violin and piano based stuff) and Many hundreads of different artists