Depends entirely on your budget and needs. I'll list off some quick top brand picks though:
CPU: Intel or AMD (SURPRISE! need more info here for a recommendation)
MOBO: Asus/Gigabyte
RAM: Corsair/OCZ
PSU: Corsair/OCZ
HD: Western Digital/Seagate
Cases: Cooler Master/Antec (lots of others though, more personal choice than other components)
Video Cards: EVGA/Sapphire
Optical: LG/Sony/Samsung
Slap together something using these brands and you will probably have an acceptable rig.
Give us more info on your budget/intended uses/upgrade preferences and we might be able to give you some specific recommendations.