I'm not very good at these genre classifications so forgive me if I oversimplify, but when I first read about dubstep, it was basically described as Techno Dub; taking electronic music and applying the same type of heavy dub mixing techniques that are applied to Reggae music.
Being a dub fan, I was intrigued, and checked out a few samplers and such and I really liked what I heard. I think the band that epitomized this sound for me was Milanese. The 'Extend' album is harsh, heavy, dubbed out bliss. Also, the Planet Mu label has quite a few dubstep compilations available as well. A good place to start.
