I currently only know of two unkown but still excellent bands. There is funny yet hard rock band psychostick (it isn't demonic voiced or yelling, just some heavy guitar sometimes) and the all-around band Sulek. Sulek pretty much is going for the variety of the eagles, but they only have one CD out so far called songs from the doctor office with the cover art done by my favorite artist/animator grey gerling/barfquestion. Psychostick has their own website and does private concerts. However, they have 3 CD'S out I think. It could just be two but i'm pretty sure it's 3. Post if you know of some unkown yet good bands that you know of/dug up.
My Dear Disco and Colourslide are pretty amazing unknown bands. You can find them both on myspace. I prefer My Dear Disco, they have a very unique sound that they refer to as dancethink.
colourslide is more of your typical alternative rock band. they were supposed to be on warped tour, but due to family issues had to cancel most of their dates. you should really check them out, My Dear Disco is getting more known, they have about 12000 friends while Colourslide has about 4500.
I get radio from Canada since I live so close to the border, and, thus, get blasted with tons of little-known, but talented bands. USS, City and Colour, and M.I.A. are all good bands.