[NOTE: Updated 24 March 2014]
I just answered a question about where someone’s folk-type band could play in the Somerville/Cambridge area, so here’s a not-comprehensive list of my suggestions:
The Arts at the Armory Cafe in Somerville – email@example.com
There are also some monthly open mics there where you can play 2 songs/pieces:
Both of those are pretty open to any sort of music – last time I was at the Sunday one a cellist who had stopped by to go the Yesterday Service classical music store in the basement played a couple of Bach pieces. Check their event calendar for any current open mics.
If you want to do your own show, Outpost 186 in Inman Sq Cambridge can be rented evenings or Sunday afternoon for $75 for 1 event or $50/ea for a series of 3 or more.. Contact: Rob Chalfen – firstname.lastname@example.org
There’s also the Lily Pad in Inman Sq, but booking a full slot can be $$$ – $70/hour, though you get to set the door charge (typically $10) and keep it. They also now serve beer and wine, though your audience can be all ages. As of early 2014 the booker is Jesse – contact him at email@example.com
Third Life Studio is in Union Sq Somerville – it is a dance studio with a grand piano, no PA. It is $25/hr for the 1st four hours, then $15/hr for longer.
Somerville does not have any specific rules about busking (unlike Cambridge, which requires a $40 permit), so you could try something impromptu in Davis Sq when the weather is better.
Gallery 263 in Cambridgeport (a couple blocks up Pearl St from memorial Drive) hosts music shows.
Out Of the Blue Gallery on Prospect St Cambridge across from Whole Foods does, too:
You might also look up opportunities at local farmers’ markets if you don’t mind playing outside:
This was off the top of my head – please list other ideas in the comments!