I recently came across the OpenCiphers project:http://openciphers.sourceforge.net/oc/index.php
It includes code that can be adapted to FPGA mining boards to do password recovery of encrypted files, crack wifi passwords, crack Bluetooth PINs, etc.
Lest one think there isn't a market for such a thing, I point to CloudCracker, a for-pay service that does just this:https://www.cloudcracker.com/
I think this bodes well for the resale value of the FPGA boards which allow you to load your own bitstreams (Ztex, X6500, Icarus - basically everything except BFL). Right now to do this you'd need the Xilinx compiler (which costs $3k) and enough knowledge of FPGA development to adapt the OpenCiphers code, but as the number of FPGA mining rigs increases, the market will be there for someone to start selling plug-and-play solutions for these sorts of applications.