The Alt Wheels show is a lot of fun - I went last year and saw a lot of interesting cars as well as other independent energy stuff. I won't be able to make it this year unless I can make a miracle happen, but it's really worth going to. To make it a complete alt. wheels experience, I took the MBTA commuter rail train in from Lowell (partly because parking is high-priced in Bean-town).
http://www.altwheels.org/
Please Join Us on Boston City Hall Plaza for the 5th
AltWheels Alternative Transportation & Energy Festival
— Friday—Saturday 28-29 Sept. 2007 —
( FREE — Fri. 9a-7p / Sat. 10a-6p)
PS: last year the RV show was on the same weekend at the Bayside Expo Center, so I also checked out some alt. living ideas (on wheels)