Like Dan Peterson, I have setup a mirror of the RubyGems repository on the same server that is an official RubyForge mirror.
http://rubyforge.planetargon.com/gems.rubyforge.org
gem install --source http://rubyforge.planetargon.com/gems.rubyforge.org postgres
The RubyForge mirror team is working on a gem mirroring solution… and in the meantime, this is my attempt to help out with the load.
Dan also noted that you could modify the .gemrc file:
gem: --source http://rubyforge.planetargon.com/gems.rubyforge.org
Thanks Danp for pointing this out… and Enjoy!