Debian Squeeze doesn't add the gemcutter source by default, instead we add it manually:

root@debian:/home/james# gem sources -a http://gemcutter.org

http://gemcutter.org added to sources

Note: Ubuntu 9.10 does have gemcutter source added by default.
Resources:
- Dr Nic ’s Hacking someone’s gem with github and gemcutter [drnicwilliams.com]

Read more: http://feeds.dzone.com/~r/dzone/snippets/~3/xuEla-Dvs3M/10185