Light rail to Baltimore - closest stops to Annapolis are Glen Burnie and BWI airport in Linthicum. For Orioles and Ravens games, many people carpool to BWI, park in an airport lot, take free shuttle to light rail stop at terminal. I don't know whether GB or BWI is closer.
Light rail via MARC train into DC - closest stop is Odenton. I think.
DC Metro, Orange Line - closest stop is New Carrollton.
Some intrepid mids figure out the bus skeds from Annapolis. There are some express buses to Baltimore, I think.