Oh yeah,
Definitely go to Antoni Gaudi's Parc Guell. Its really great. Its a little outside the center part of the city, but its a beautiful park with gaudi's architecture, sculputres, etc, try to go towards the end of the day/sunset as its really nice and the crowds go down a little bit. You may want to spend longer there though.
http://www.parkguell.cat/en/
Dali Museum. There's a tour I took which was pretty good. We went to Girona at first and then the Dali Museum. Honestly, I thought Girona was a little boring but the #1 restaurant in the world is currently there. We booked on Viator. They just resell packages from this company called Julia Travel. They have an office a few blocks from Placa Catalunya.
http://juliatravel.com/destinations/barcelona/
Sagrada Familia. You have to get something with front of line tickets, the queue is long as FUCK. Its also not really walking distance to the main part of the city.
I thought La Rambla kinda sucks. A bunch of pickpockets, hucksters, etc. Gothic Quarter is very cool.
Go to the beach. Chill. The Port Olympic has nicer restaurants with views.
The famous drink is the gin and tonic there, they do it differently with aromatics in a large cup. really great since its so hot/humid.
This is the Pinoxto Bar.
http://www.yelp.com/biz/pinotxo-barcelona It gets SUPER crowded you just have to be patient, wait behind someone eating at the bar and one of the waiters will tell you you're next.
The things to eat in Barcelona:
Seafood- especially razor clams. Also see if you can find Percebes somewhere. They are barnacles from Galicia and they are really fucking good. Octopus is really good as well.
Tapas- a given. Find some good spots.
The Turkish kabobs are really good. The Doner kebaps and stuff like that.