Computer History Museum in Mountain View has a pretty cool 1.5 hr tour. You can see parts of a Babbage Difference engine, ENIAC, CRAY 1, 2's, One of GOOG's early server racks, washing machine sized hard drives, etc... It's a lot of fun.
..and all the other goodies that was located at the Boston Computer Museum. Someone decided to plow it over when they were just so happening to put an interstate underground. Oh well. The commute to the airport is wicked fast now.