sorry dafoomie, I'm gonna contradict:
for the love of

ing god, don't go to Mike's Pastry. it's a tourist trap. it's not bad, but it's not amazing either - if you're looking for italian baked goods, search yelp.com for a lesser known place, with likely better desserts and DEFINITELY a shorter wait, compared to the line of n00bs at Mike's.
Since you're in Cambridge, it's worth walking around Harvard Square, but like dafoomie hints, it's a pretty faux-urban/hipster-consumer collegetown with an air of elitism, given that its, oh ionno, harvard kids? Since you're there with the GF, you might want to research LA Burdick or Sweet Cupcakes, both in Harvard Square.
As for pasta, like dafoomie says, hit up the north end for italian restaurants. avoid big-name seafood places, as they're likely tourist traps with mediocre food (to add to Union Oyster House/Barking Crab, stay away from Legal Seafoods).
The next subway stop from Harvard is Central Station, also considered Cambridge area. This place is odd, as it's very near Harvard, and houses several MIT/Harvard affiliated folk, yet is overrun by sketchass hobos and weirdos. However, there are a couple decent nooks worth checking out. Do your some research on yelp again, as I don't know what sort of places you're into.