America On Wheels Museum has 75 bicycles, motorcycles, automobiles and trucks. They have an impressive collection of Mack trucks. It also has the 1889 Nadig Gas-Powered Carriage, one of the first cars in the US.
Small but nice. They have three large galleries and a handful of smaller ones. They have a restoration area that's very interesting, as well as a cafe and art exhibit. If you're in Allentown PA, it's definitely worth hitting up. Same with the Mack Truck Museum.