From Yelp
"Cosi is a great sandwich chain. The fresh ... Cosi is a great sandwich chain. The fresh bread is yummy. Yes, this one in particular is crowded, and yes it's doesn't have mind blowing atmosphere, but it has free wifi and constant freshness in the bread department. ..." - Feb 23, 2010
Unfortunately I think that almost any restaurant or coffee shop will be crowded. It would be best if we could get a room at Harvard or MIT, but failing that it is possible to reserve a room at the main branch of the Cambridge Public Library. It would be worth looking into for future meetups, their info can be found here:
http://www.cambridgema.gov/cpl/aboutus/contactinformation.aspx
It has not been crowded the times I've been there. (Sadly I do not live in Cambridge, I just visit periodically, so I am not actually likely to make it to a meetup there!)
The Sunday Cambridge meetups, which happen on the first and third Sunday of each month, are now at 2:00 pm at Cosi, near Kendall Square. As discussed at the last meetup, we've changed the location because the old location was becoming too crowded, and the time to allow the meetup to go on longer before people have to leave.