We usually meet in building 66 in room 168 (or one of the rooms next to it); if you enter at the "point" on Ames St, it is the first classroom on the left.
To get to the meeting, you'll first need to get get to MIT.
Here's a campus map, with Building 66 highlighted (it's the triangular building next to Ames St).
The closest MBTA (Red Line Subway) stop is Kendall Square. It is in the upper right hand corner of campus map just under the legend "Kendall Square". It is also possible to take the #1 MBTA Bus to 77 Massachusetts Ave. which is Building 7 on the map above and walk inside through buildings 7, 3, 10, 4, 8, 16, and 56 to building 66.
The closest MIT parking lot that you can easily park is the Hayward St. Lot. The Hayward lot is free and open to the public on weekends and after 4pm on weekdays (along with most other non-gated parking lots at MIT).
It's near the corner of Main St, and Hayward St. (at this point Main St. is essentially one-way east bound (towards Boston)).
If you're coming from I-93, I think the best way to get to the lot is to take the hard right turn onto Memorial Drive as soon as you finish crossing on the Longfellow Bridge. Once you're on Memorial Drive take the first right (Wadsworth St.) and then turn left onto Amherst St and right onto Hayward St. The lot is on your left.
The west-bound side (towards Cambridge) of the Longfellow Bridge is closed to traffic for the next year or two.
If you're heading east bound (towards Boston) on Memorial Drive, I think there's a break in the median strip with a sign that says "Kendall Square", that's the turn for Wadsworth St.