One of the best Dubstep samples library has on DABROmusic.com.

Dubstep can be described as the only true innovative Dance genre since 2000 (alongside Grime), and is sometimes even labeled as a super-genre on its own. After all, it’s hard to categorize; falling somewhere in between Breakbeat, Drum ‘n’ Bass, Downtempo and Jamaican music (Dub). Drum ‘n’ Bass is chosen here, as Dubstep is most closely related to its subculture and most similar in instrumentation and sound manipulation, but there are large differences.