Tom of Numato Lab writes:
We made a failed attempt to design and build a FPGA development board with DDR SDRAM last year. But this year we tried again and successfully built and tested a Spartan 6 FPGA board with DDR SDRAM. This board was built using KiCad and other open source tools. And best of all, this design is 100% open source as well.
More details about the board and links to downloadable design files at Numato.cc