After a lot of thought, I've decided to release my FPGA files. I've put a lot of time and effort into designing a minimum-cost FPGA board. I've been through 2 prototype cycles, but this stuff is expensive! On my student budget, I can't afford to spend any more on a project that may or may not pan out. When I burned out my last Cyclone IV, I was like, "I'm done!" The design is 98% there, I believe.
Thanks to fpgaminer for lots of advice.
Here's a link where you can download a zipped folder. It contains pictures, a Bill of Materials with cost breakdown and suppliers, a circuit board layout, and links to all of the Altera documentation I've been using.http://www.filedropper.com/pcbtoupload62611
You will need to download expressPCB's free CAD software to view the board layout. I hope that knowledgeable people with deep pockets can take this project and finish it. GPU mining is way too wasteful. There are probably still bugs in this design.
I used a Cyclone IV EP4CE115F23C8N FPGA. It offers good performance for a decent price. We have already hit 80 Mhash/s with it, with no cooling other than a passive heat sink. The heat is the limiting factor. With better cooling, we'll be able to add a second core and run it faster. I'm thinking ~140 Mhash/s.
As you can see, the board is very small. It would be very cool to make a cast aluminum box for it and fill the box up with mineral oil. That would give 100% reliable, cheap, quiet cooling. This guy may be able to hook one up:http://forum.bitcoin.org/index.php?topic=20404.0
Feel free to send a few bones my way if you like the project!