I highly doubt there are many Kpop fans on here, but I'll go ahead and see.
Gathering all Kpop fans! =) Major Kpop companies include...
SM Entertainment (DBSK, Super Junior [+ Subgroups], SHINee, The Grace, SNSD, Kangta, BoA, etc.)

YG Entertainment (Big Bang, 2NE1, SE7EN, Gummy, etc.)

JYP Entertainment (Wonder Girls, 2PM, 2AM, Bi/Rain, g.o.d., etc.)

DSP Entertainment (SS501, KARA, A'st1, etc.)

Of course there are many other groups and solo artists out there including Epik High, The Melody, Peppertones, and Clazziquai that don't necessarily fall into the Kpop category, but they are welcome as well. So, uhm. Discuss, fangirl, all that stuff.