As I was doing some research, I found this list that Uwishunu posted. It's a pretty good list of restaurants/bars that offer outdoor seating, but I have a few additions:
University City
1. Biba Wine Bar
I have yet to try this place out but if it's anything like Tria, I'm sure I'll love it. The deck is under construction as we speak and should be done any day now...and will seat 12 lucky people.
Rittenhouse Square
2. Vango
They have a cool rooftop bar (one thing we are DEFINITELY lacking here) and there's a DJ on the weekends and gets pretty dance-y...which I like. And as you can see, there are pretty awesome views.
1. Twenty Manning
I love this place - the food is good, it's well designed and has that cool, neighborhood-y feel to it. Plus, under the awnings are spritzers that will spray you lightly with water to keep you feeling cool on those hot Philly summer days.
1. Tequila's
This photo doesn't show it, but when it's nice out, they put tables and chairs along the front of the building. There isn't room for many, but it's a nice spot to sit. The food here is also delicious and the margaritas are even better! They have a pretty good happy hour too.
Midtown Village/Gayborhood
1. Graffiti Bar at Sampan
I've been to Sampan a few times but haven't yet tried out their backyard bar. It looks cool - and at least I know the food and drinks are good.
1. Raw
I almost forgot about this place until Eric reminded me! I've only eaten here once but I remember the tuna tartare was really good. The courtyard is really nice also - and pretty spacious. I definitely need to hang out here more often this summer.
Bella Vista
1. Creperie Beau Monde
I had to to include this place - the crepes here are delicious and the bar upstairs (L'etage) used to be my favorite dance place in the city. The music is still pretty good, but it's been feeling really young lately. Or maybe I"m just getting old...
1. Bistro La Minette
This is one of my favorite restaurants in Philly. The food is incredible and in the summertime they play French movies in their courtyard. I think there are some outdoor seats in the front of the restaurant as well.
Northern Liberties/Fishtown
1. Silk City Beer Garden
Haven't been yet, but sounds good to me! It's the only beer garden in Philly right?
Anybody have any other suggestions??