I'm sure there's lots, but it also depends on your definition of success. Here in Chicago we've got groupon, threadless, braintree, thinkorswim, 37 signals, or

I'm sure there's lots, but it also depends on your definition of success. Here in Chicago we've got groupon, threadless, braintree, thinkorswim, 37 signals, orbitz, and then, of course, a number of places which have cashed out to acquisitions (like feedburner).