Try this link from Wikipedia: http://en.wikipedia.org/wiki/List_of_MTA_Maryland_bus_routes. Do keep in mind that Wikipedia's information is provided by users, so there is always a chance that the information has not been verified or is not correct. That said, I have found much of Wiki's data to be useful and correct for the research that I have done.
Also, here is MTA's website: http://mta.maryland.gov/
Residential and Commercial Real Estate