Note to Brian:
Depends where you want to work. Brigham & Women's? Brookline, Brighton, or maybe even Allston. Cambridge near MIT? Kendall, maybe Central if you can find an ok place. Harvard? Harvard Sq., Porter, Inman, Union, Davis. Same answers for Tufts. It seems like a lot of private research can be found in Cambridge, too. But you don't want to take a job in the Longwood area and find a place in Somerville. Not that the commute's all that bad - it certainly doesn't stop yours truly from hanging out with Miss Piccola-Fales and the good doctor - but it's not something you'll want to be doing during rush hour.
Although Pammy could probably give you a better idea as to the bus service.