I dunno : i've lived in san jose for a long time and found the vast majority of the things i did were very specific with the friends i hanged out with.
San Jose ( SF Bay area ) is unique because it's home to many things. The Tech Museum of Innovation, 2 MLB Baseball Teams, 2 NFL Teams, 1 NHL team, 2(or more?) Minor league teams, 1 MLS Team. There is Great America and if you're interested and have connections can find almost any tech company in SJ. I got to tour the old Diamond Multimedia campus (one of my parents worked there when i lived up there.. and they were still around) and that was pretty neat. It's right near the Great America parkway too. SJSU hosts numerous events throughout the year so you can sometimes lookup their calendar for something to do. San Jose also has a ton of cyber cafes if you're into gaming. I like euphNet myself (less scary then rivaloution imo since it's not gang owned

) which is in sunnyvale, San Jose (beressa i think?) and soon redwood city if your up in that neck of the woods. Mini gold places are pretty abundant (golfland) as are bowling and other such activities. There was an indoor paintball arena inside the san jose area near capitol, i'm not sure if that's still around. There is an outdoor place that i remember being cool in the fremont hills (i think) as well as Santa Cruz. (driving on 17 can sometimes be an event in itself). There is Speedring and malibu grand prix for gokarting (malibu is outdoors). Culture wise SJ/SF/Oakland is pretty rich. SJ Symphony, SF Symphony, I believe STOMP! has a permanant setup in SF, and if not they come to the flint center at Cupertino often enough. Other musical sites in the summer includes the Stanford Jazz festival, and numerous Drum and Bugle Core shows (Santa Clara is home to 6x World Champion drum and bugle corps). There is of course the touring orchestra's at Flint, MV Center for performing arts, etc. Also the San Fransisco Opera hall, and many productions are held throughout all three cities. SJ Ballet company puts on several productions throughout the year as well. You can visit the numerous college campuses nearby (and perhaps party..)
Valley Fair, The Great Mall, Santana Row (right next to valley fair), and Stanford Shopping center are all pretty popular too. After living in socal for sometime i cna't remember the names of decent Bars and Clubs but im sure there has to be a couple around.
There's a lot to do around SJ for a lot of different people... i would say Go to professional sport games (even if you dont like watching the sport on tv..) they tend to be fun in groups. One friend of mine hates hockey, but loves comming with to sharks games. The logic i've never understood but apparently they are a lot more exciting in person and that's enough to make it interesting enough. Try out some of the tech specific sights, and do the SF sight seeing thing with friends. I've seen the golden gate bridge a million times, but it was fun being all touristy with friends. And try out new things, my buddies and i are planning on going to a shooting range when we all get back in SJ. Just cause it's something we haven't done before.