Stanford and UIUC probably win in terms of startups just because of number of grads in the startup world, but I'm perfectly happy here at Carnegie Mellon...the job fairs are full of all the big-name software companies as well as some startups, we have a Google office literally next to campus, and the school is diverse enough that if you ever tire of the CS personality there are plenty of liberal arts folks, as well as a whole city full of college students. Granted, the weather isn't that great, but the classes are challenging, the professors are great, and the people are nerdy.
Of course, most everyone here is going to be pushing their alma mater, so my advice is to visit as many of the major CS schools as you can. You get a comparable education at all of them, I doubt one is that much better than the rest, so go with whichever one feels right. Ask random students walking to class about the best and worst thing about the school, ask about the courses and workload, and most importantly see if you like the area: distance from home, climate, how big-city it is. You're going to need to live there for 4(ish) years, you want somewhere that you'll enjoy living in so that you don't lock yourself in your room and burn out.
Oh, and if you're visiting CMU drop me a line, I'll show you around (current student).