my band is pretty decent, check us out, you may dig us:
www.myspace.com/invectionmetal
in terms of other new good bands:
Warbringer (Waking Into Nightmares, not the first album)
Evile (Enter The Grave, not the new one)
Bonded By Blood (Feed The Beast, not the new one)
old bands:
Demolition Hammer (anything except Timebomb, a very groovy thrash with a hint of death metal, skull crushingly heavy)
Morbid Saint (really fucking fast and evil, their album Spectrum of Death is all they released but check it out, the demos are shit)
Epidemic (a fairly unknown bay area thrash band but their album Decameron I think it's called is really good, their album before The Truth of what will be (or something) is also pretty good but a bit more raw)
Devastation (Texas band, Idolatry is an insanely heavy album that rumbles along yet has super fast db; their other albums aren't nearly as good)
Razor (Shotgun Justice and Open Hostility are really good and aggressive, the earlier ones are just typical old school style thrash, not too great nor is Decibels)
To be honest those are the best of the old bands that I actually still listen to, I could name off a bunch more that are good but only those have regular rotation in what I actually play
Of course the big bands are still great but those are obvious:
Metallica
Megadeth
Anthrax
Slayer
Testament
Exodus
blah blah blah