Update 6/17/12: Another successful Father's Day in Princeton. Yankee Doodle Tap Room had some menu changes but everything was pretty good and it has a great outdoor patio. Princeton is still an ideal little day trip from the Philly area - one hour from Center City; lovely, walk-able main drag on Nassau Street and in Palmer Square; lots of shops and restaurants to check out. Stop at the Bent Spoon for ice cream!
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Philadelphia offers an endless list of things to do on the weekends, but sometimes it's just nice to get away. If you're looking for a quick day trip with good food, shopping and atmosphere, my vote is for Princeton, NJ.
We have spent the last few Father's Days in Princeton because it's a convenient meeting spot for both our families. My brother lives there and never fails to pick out a solid restaurant for brunch. This time we went to the Yankee Doodle Tap Room at the Nassau Inn.
The Inn itself is beautiful and worth a stroll through just to see the old, dark wood interior that is nothing short of Ivy League material. I imagine it's one of the priciest places to stay in town, but convenient for Philadelphians, Princeton is only 50 mins away so there's no need to worry about getting a room.