I recently got some PCIe SSDs based on FPGAs, a 365GB ioDrive2 for $33 and a 2.6TB ioMemory PX600 for $68. The ioDrive2 is based on a Virtex 6 and the ioMemory a Virtex 7. The ioDrive2 could be repurposed by designing a board to fit the memory board sockets. Other than that, the only other reuse I can think of are those that would do well with a large FPGA coupled to a large amount of Flash memory, maybe some crypto mining or AI would fit that description with the Flash containing massive lookup tables.
From my understanding, the Virtex 6 can be used with the free unlocked "Windows 10" ISE. The Virtex 7 might as well but I think it's intended for Vivado of which only the paid version supports it.