Good places to live near Harvard (Boston)

Hi everybody,
I'm going to do research at Harvard from end of august to february. Currently I'm searching for a room to stay (at craigslist and a Harvard website), but I don't have any idea about where are nice areas to stay. Can you give me any advice? Shouldn't be too far away from Harvard Law School, not too expensive (up to Protected content for a room/apartment) and in a lovely area. I'll be happy for any ideas,

Greetings,
Ben