Each of these sites typically shows you their roster and has information on each band. You can also contact publicists here to request an interview.
Mazur PR works with a lot of heavy acts such as:
Demons & Wizards
Diesel Machine
Glenn Hughes
Ivory Tower
Kansas Liquid Tension Experiment
Lana Lane
Michael Monroe
Mortiis
Neurosis Rhapsody
Rockbitch
Luca Turilli
Udo Dirkschneider
Venom Steve Walsh
Yellow Machinegun
A full service publicity group. They handle KidFilm and The USA Film Festival just to name a couple of things they do.
MSO is quite large and handles a variety of acts: