There are a couple of ASIC designs available for sale, but no ready made chips... I think the best option at this time would be to wait for a fast SHA-256 chip to pop up on Octopart, then warm up your soldering iron
Only way to really profit from this is: -10 pile large amounts of USD to MtGox (there are some fees involved) -20 trade USD to BTC on MtGox -30 trade BTC back to USD on bitfloor -40 withdraw your USD from bitfloor (there are some fees involved) -50 goto 10
Also note that steps 10 and 40 might have significant waiting times.