If you are deploying to a server, or you do not want to wait around for rdoc and ri to install for each gem, you can disable them for gem installs and updates.

Just add the following line to your ~/.gemrc or /etc/gemrc:

gem: --no-rdoc --no-ri

or

gem: --no-document

or if want to be more specific,

install: --no-document
update: --no-document