The San Jose Tech Museum is located in downtown San Jose right off Highway 87 on Market St. There is no free parking, so expect to pay anywhere from five dollars to $20 depending on where you park.
There are numerous rotating tech exhibits at the Tech Museum. One of the newest exhibits that has just opened is called "Net Planet" and focuses on the Internet, past present and future. There are interactive displays on how the internet works, including an internet arm wrestling exhibit and one on how "avantars" (online identities and characters) are developed.
The museum has many other exhibits too, including one that describes how microchips are fabbed, one that talks about cells and biotechnology, and one that features the gadget of the week (they had segway scooter demos when I went).