[farresito]

Some guy started a series some weeks ago on designing a CPU for an FPGA: http://labs.domipheus.com/blog/designing-a-cpu-in-vhdl-part-...

For those interested in a more complex processor, RISC-V seems to be a processor on par with ARM in terms of features: http://riscv.org/

[kjs3]

Both of these are excellent projects to check out if you're interested in such things. And, bonus, the RISC-V folks have produced an open source, modern manufacturing process, 1GHz core that I hope is a game changer in open source hardware. It's not quite on par with ARM (lacking the billions in investment), but it's in the ballpark and it's the real deal. Definitely worth keeping up with.