By the nature of the business, most of these shops are secretive. But there are some technology vendors out there building products based on FPGAs. Stone Ridge

By the nature of the business, most of these shops are secretive. But there are some technology vendors out there building products based on FPGAs. Stone Ridge Technology is one of them (I saw an article in magazine, have no experience myself)! I have heard that FPGAs are mainly use to parse and normalize incoming market data. For example a data feed coming from NYSE in the ITCH format. Other hedge funds are also using hardware based solutions. But more likely GPU based solutions for number crunching. If you are interested I would recommend checking out the forums at wilmott.com or at the Nuclear Phynance [sic] board. Wilmott magazine also has had a few articles on models written in CUDA for pricing options etc.