I am not certain of any dedicated folk venues, hopefully someone chimes in with some suggestions. Often the clubs around here will do acoustic nights so I would be on the lookout for that stuff.

I checked out your myspace page and your music sounds great, please post here if you end up booking any shows around here. Also you may want to come to one of the networking mixers. Here is some info www.worcesterite.com/mixer

It's not folk or bluegrass but I'll be playing an acoustic set tonight at 9:00 at the Lucky Dog on Green Street. We do blue, country and rock and roll. Come down!

Holly, while not really a traditional venue (or coffee house), The Green Rooster Coffeehouse at the United Congregational Church is worth keeping your eye on as they really get some pretty good stuff every once in a while. They are almost exclusively folk music. They are on Institute Road right next to the Worcester Auditorium.

http://www.ucc-worcester.org/greenrooster/

Also worth looking for when they play in the area are two of the best newer style folk acts around who both happen to be from the area in The Accident That Led Me To The World and The Points North. Both bands are worth going out of your way to catch. From their my space pages you can develop a bit of a road map for exploring what the region has to offer for folk music.
http://www.myspace.com/tatlmttw
http://www.myspace.com/thepointsnorth

The Accdent just shot a great video for the title track to their latest album, The Island Gospel:

There used to be a great place called the Round Oak, but it shut down years ago.

Fiddler's Green at the "Worcester Hibernian Cultural Center" next to the Dive Bar on Temple Street has open traditional Irish music sessions every Sunday afternoon, though the site appears not to be updated:

http://www.fiddlersgreenworcester.com/