Anyone noticed this one:
http://enterpoint.co.uk/products/spartan-6-development-boards/xc6slx150-x2/
Shop: http://www.enterpoint.co.uk/shop/en/93-xc6slx150-x2-coprocessor.html
2 XC6SLX150, 400 MH/s, £300.00 tax excl. => ~1.2US$ / MH/s

This one is less cost-effective, but higher integrated:
http://enterpoint.co.uk/products/asic-development-high-performance-computing/merrick-3/
Shop: http://www.enterpoint.co.uk/shop/en/98-merrick-3.html (sold out)
24 XC6SLX150, 4.8 GH/s, £6,500.00 tax excl. => ~2.2US$ / MH/s

The first one got my heads-up, since it comes for a price comparable to Icarus, which currently is the most cost-effective and commercially available FPGA miner.