I've just republished tarball of libgmp-ruby (Ruby bindings to GNU Multiple Precision Arithmetic Library). It's a very old package (literally Ruby 1.6 old), but the server hosting it died and I never quite got to republishing it before.
It is available for download in tarball format. To compile the package use:
$ ./extconf.rbIt used to build Debian packages. I don't know if they still build or if some tweaking is necessary. GEMs are not provided, as the package is older than Ruby Gems. Some day I'll get to updatng it and providing DEBs and GEMs.
$ make install