Monks cafe is the #1 spot to get a beer in philly and happens to be right nearby Rittenhouse. They are also known for their mussels and frites. I prefer the duck.

Other spots to checkout in Rittenhouse: jose pistolas, black sheep, good dog, fado, misconduct. Fado clientele will vary greatly depending when you go, im told its a college bar in the evening, but i usually meet European soccer fans there earlier on the weekends.