I agree Jen, subtle advocacy can work. I have been banging on about Linux here at work for the last 4 months. This week however I just brought some Ubuntu, Kubuntu, Edubuntu and Open CDs into work and left them in my in tray. 4 of them have already gone with little effort on my part.
Then there’s my password change policy. When someone asks for a password to be reset on a system I look after, I change it to “Ubuntu” followed by a number. They ask how to spell it, I hand them an Ubuntu CD. Easy.