Monk's Cafe
This place needs no introduction among Philly's beer lovers.
Monk's specializes in bringing Belgium to the USA. It's famous Beer Bible contains hundreds of brews (you can buy your own copy to keep track of what you've tried), and the draft list is ever-changing. The food is amazing - they're best known for their mussels and fries, but for those of us not as excited about seafood, their sandwiches and burgers are delightful. Weirdly, I actually love their veggie burger even more than their normal one! And the dipping sauce for the fries....well, let's just say that the list of things I wouldn't do for a bottle is much smaller than the list of things I would.
No matter the style of beer you enjoy, they have something for you. However, if you're a Belgian style or sour fan, this place is paradise.