Some links for you:

  * https://hackaday.io/project/18491-worlds-first-32bit-homebrew-cpu 
  * https://hackaday.io/project/178826-pineapple-one
  * https://hackaday.io/project/18859-risk-vee
  * https://hackaday.io/project/168894-rv7400-computer 
  * https://www.youtube.com/playlist?list=PLEeZWGE3PwbZTypHq00G-yEX8TEI95lw4

There are lots of soft cores available for RISC-V too of course.