An initial port of the GNU Ada Translator (GNAT) is available for the Hurd.
The goal of this project is to continue improving and polishing that port and getting it integrated in the upstream GCC repository. It requires implementing some explicitly system-specific stuff in GNAT (mostly in its runtime libraries), and for that also address a number of issues in Hurd and other libraries. Knowledge of Ada is a must; some Hurd knowledge will have to be acquired while working on the project.
Designing and implementing language bindings is a follow-up project.
Exercise: Fix one of the known issues of GNAT on the Hurd.