Since Mike and Chad have already posted theirs, here’s my gem list | grep ‘^[ ]’:

actionmailer (1.3.1, 1.2.5, 1.2.3, 1.2.1, 1.0.1)
actionpack (1.13.1, 1.12.5, 1.12.3, 1.12.1, 1.9.1)
actionwebservice (1.2.1, 1.1.6, 1.1.4, 1.1.2, 0.8.1)
activerecord (1.15.1, 1.14.4, 1.14.3, 1.14.2, 1.11.1)
activesupport (1.4.0, 1.3.1, 1.1.1)
audioscrobbler (0.0.1)
badger (1.0.0)
barcode (0.2)
BlueCloth (1.0.0)
builder (2.0.0)
capistrano (1.2.0, 1.1.0)
capistrano-ext (1.1.0, 1.0.1)
cgi_multipart_eof_fix (2.0.2)
cocoa_dialog (0.0.2)
color-tools (1.3.0)
cooloptions (1.1.0)
daemons (1.0.4, 1.0.2, 0.4.4)
dhaka (0.0.6, 0.0.5)
diff-lcs (1.1.2)
fastercsv (1.0.0)
fastthread (0.6.2)
fcgi (0.8.7, 0.8.6.1)
gem_plugin (0.2.2, 0.2.1)
greenbar (1.0.1, 0.2.1)
gruff (0.2.8, 0.2.4, 0.1.2)
hoe (1.1.6, 1.1.2)
hpricot (0.4)
instiki (0.10.2)
json (0.4.2)
keybox (1.0.0)
keyword_search (1.0.2)
libxml-ruby (0.3.8)
madeleine (0.7.3, 0.7.1)
mailfactory (1.2.3)
memcache-client (1.2.0, 1.0.3)
mime-types (1.15)
mongrel (1.0.1, 0.3.13.4, 0.3.13.3, 0.3.12.4)
mongrel_cluster (0.2.1, 0.2.0)
mysql (2.7)
needle (1.3.0)
net-sftp (1.1.0)
net-ssh (1.0.10, 1.0.9, 1.0.8)
open4 (0.9.1)
paginator (1.0.8, 1.0.7, 1.0.5, 1.0.0)
pdf-writer (1.1.3)
peggy (0.1.0)
piston (1.2.0, 1.1.1)
radiant (0.5.2)
radius (0.5.1)
rails (1.2.1, 1.1.6, 1.1.4, 1.1.2, 0.13.1)
rails_gem_plugin_shim (1.0.0)
rake (0.7.1)
rcov (0.7.0.1)
RedCloth (3.0.4, 3.0.3)
rmagick (1.14.1, 1.11.1, 1.10.1)
rspec (0.6.4, 0.5.13)
rubyforge (0.3.2, 0.3.0)
rubygems-update (0.9.0)
rubyosa (0.1.0)
rubyzip (0.9.1, 0.5.8)
ruport (0.6.1)
scruffy (0.2.2)
sources (0.0.1)
spacesuit (1.2.0)
syntax (1.0.0)
tattle (1.0.3, 1.0.2, 1.0.0)
termios (0.9.4)
Text (1.1.0)
transaction-simple (1.3.0)
twfy (1.0.0)
twitter (0.0.2)
tzinfo (0.3.2, 0.3.1)
xhtmldiff (1.0.0)
ZenTest (3.4.1, 3.2.0)