This is brilliant: Ishkur's Guide to Electronic music.
Most of my collection falls in the following categories (with most being House and Trance) if you were interested in such things:
House: Classic, NRG, Progressive
Trance: Classic, Dream, Progressive, Anthem, Ibiza, Goa
Techno: Hard Acid
Hardcore: Rave, Happy
Down tempo: Trip hop, Ambient Techno