gem environment
This will pop up a handy list like this:
RubyGems Environment:
- VERSION: 0.9.4 (0.9.4)
- INSTALLATION DIRECTORY: /usr/local/lib/ruby/gems/1.8
- GEM PATH:
- /usr/local/lib/ruby/gems/1.8
- REMOTE SOURCES:
- http://gems.rubyforge.org
Your gems are nicely tucked away within your GEM PATH directory