So, I'm somewhat addicted to coffee, so let me give you a rundown.
On Campus:
On the Dining Plan:
In Fresh Food Cafe: They have drip coffee. If you bring a thermos you can definitely take your coffee to class. However, to be honest, the coffee's just not that great. So it's free but that's something you battle with.
Einsteins/Super-Depot (The food place in Wolman) also has (I think only) drip; but I haven't had it since Freshman year so I can't be counted on to tell you the quality.
Pura Vida (In Levering): Has Drip as well as espresso. You can get this with dining dollars, which is convenient. They also have a selection of snacks... The coffee is so-so, but definitely the best option for coffee that's on the dining plan.
On Campus but not on the dining Plan:
Cafe Q. Located in the library: convenient, good coffee, long lines btwn classes. I think cafe q is the best on campus choice for quality. Espresso & Drip. The only toss-up is the espresso really varies based on who is making your coffee... ah well.
Assorted coffee stands are also available throughout campus, one is in Bloomberg and one was in Gilman but I am not sure what will happen to that one what with the remodeling of Gilman this year.....
Off Campus:
Barnes & Noble Starbucks: Normal starbucks selection, convenient because it's in the bookstore, so it's kind of on campus. In the Charles Commons Building.
Starbucks on St Paul: Normal starbucks, however it is unfortunate that they didn't set their store up well b/c there are no really good places for studying.
Carma's (as mentioned by Julia): has a great coffee (espresso/drip) and also great food. Unfortunately Carma's is teensy, so camping out there for work isn't much of an option, unless its nice outside.
One World Cafe: Located on University. Has espresso/drip and also a bunch of delicious veggie food =) YUM. The coffee is kind of hit or miss though... the drip is good so if you like that it might be best to rely on.
Okay those are the main coffee places, you can also find coffee at Donna's, Paper Moon and possibly along Charles depending on which places are open... (this changes frequently, oddly enough)
Okay goodluck! Get your caffeine!