"Mainstream" is basicly whatever is selling at the time. Maybe it's the real deal, maybe it's not. Sometimes you hear something and think "oh, what is this crap?" then you look back a year or two later and think "woah, they were trying to make a point, weren't they?" (see: Reel Big Fish).

So I try and keep an open mind. Right now I'm listening to a band out of Gainsville Florida called Rolling Buck 7, maybe the next song that iTunes randomly plays will be Billy Joel, maybe it'll be Five Iron Frenzy. Actualy, now that the song has actually changed, it was Primus (suprise, suprise). Anyway, my point is "keep an ear open." You hear things better that way.

And now for some linkage...
The Bocce Wagon (Shameless self promotion).
Clutch
Scissorfight
Bruce

Anyway, root around your area, check out flyers, see who's playing, you'll find cool music, I swear.