I finally found a nice simple way to update Ruby Gems when you’re behind a proxy thanks to Nigel Thorne (blog now dead).

set HTTP_PROXY=http://[username]:[password]@[proxyserver]:[port]

or if your proxy doesn’t use authentication

set HTTP_PROXY=http://[proxyserver]:[port]

Since the Gem software looks for the upper case HTTP_PROXY variable when executing it’ll take this from the environment variable and work it’s magic. This makes everything a lot simpler and gives me one less reason to use NetBeans, as I never liked it inability to choose from gem updates.