Well, most of known soloists was mentioned already... xD Maybe you should check Se7en as well? And I think Taeyang (Big Bang)'s solo stuff is pretty popular too. From male groups I definitely recommend 2AM, F.T Island and SHINee.
I guess you may be interested in TRAX since they're true rock band even though their latest release was rather very pop-ish. I recommend them too then.