So the following is a list of gems included with Leopard – by default.

actionmailer (1.3.3)

actionpack (1.13.3)

actionwebservice (1.2.3)

activerecord (1.15.3)

activesupport (1.4.2)

acts_as_ferret (0.4.1)

capistrano (2.0.0)

cgi_multipart_eof_fix (2.2)

daemons (1.0.7)

dnssd (0.6.0)

fastthread (1.0)

fcgi (0.8.7)

ferret (0.11.4)

gem_plugin (0.2.2)

highline (1.2.9)

hpricot (0.6)

libxml-ruby (0.3.8.4)

mongrel (1.0.1)

needle (1.3.0)

net-sftp (1.1.0)

net-ssh (1.1.2)

rails (1.2.3)

rake (0.7.3)

RedCloth (3.0.4)

ruby-openid (1.1.4)

ruby-yadis (0.3.4)

rubynode (0.1.3)

sources (0.0.1)

sqlite3-ruby (1.2.1)

termios (0.9.4)

Rails, ferret, capistrano, pretty cool.

[Above list lifted from MacOSforge]