Some of these have probably been recommended above, just consider it as kind of boldfacing them on your "to-download" list:

Infected Mushroom
Growling Mad Scientists (or G.M.S)
Shpongle
1200 Micrograms
Astral Projection
The Crystal Method
Chemical Brothers
Antiloop
Andy Hunter (the Life album)
Paul Oakenfold
Juno Reactor
Ferry Corsten
ATB
Daft Punk
Groove Armada

That's a pretty disparate list, but there should be something for everyone there. I'd also suggest getting compilations of various artists, those usually include some of the better tracks and you can kind of go from there.