Adavant, probably the smallest band i listen to, only 385 fans on facebook and you cant find their songs anywhere on youtube.
others include, Northern Sword, Apokefale (no these guys are the smallest, only 26 fans) and The Omega Experiment (slightly larger and are supporting Devin Townesend later this year and are the only band that i can think of that sounds like him).
Larger bands i like but nobody seems to of heard of are, Dave McPherson, Alghazanth, InMe, Cynic (large band but very under the radar)etc.