The Plateia Exarcheia square and nearby streets like Solomou have lots of clubs and bars. You don't have to be a left-leaning student to feel welcome.
Taximi
Cnr. Harilaou Trikoupi and Isavron
210-363-9919
Rebetiki Istoria
181 Ippokratous
210 2587455
One of best rebetica clubs, often open in summer when most others are closed.