I just wanted to point this out. You have to be political, and smooth or it can backfire on you.
The best way it to get your manager excited without letting them know you have too much emotion invested. Make them think it was their idea to move to rails.
Great advice and awesome post! I had to convince management sort of like that. Thankfully I do get paid to develop in Rails all day, but it's solo and I since I learned solo and work solo I long for a team environment like in my systems admin days. It's much funner to work with a bunch as enthusiastic as you, and share knowledge in the same field.
James is correct, the best way to propogate RoR inside a corporate environment is to show the great effect it can have on your programming productivity.
I have a friend who installed an RoR app on a spare Linux box in his cube & now has nearly 100 engineers accessing it on a daily basis. He's prepping his boss to go to bat for him by describing its mission-critical natue.
Before starting to use Rails at work, I tested the waters by asking my boss to buy Pragmatic Programmer's Agile Development book for me. His reaction was, "Oh cool! I've heard about Rails!" Later, he came to me with a project that he thought (correctly) would be good to do in rails.
Then he left the company. The person who took over for him had previously made it clear that, if it had been his decision, the project would have been done in PHP instead of, "That weird Ruby crap." He was a great guy and a fine boss. He just wasn't as comfortable with new technology as the other.
Then I was found by someone who really wanted to start his team working with Rails but couldn't find anyone in the area who knew anything about it. When the company offered me a 60% raise to do Rails programming, I took it without a backward glance.
The first three months at the new job, they had me working in PHP, because that was the existing code base. I'm doing almost exclusively Rails development now, though I still have to keep tabs on what's happening with the PHP end.
Moral: Rails can get your fired and it can get you hired too. But keep your skills in other things up to date!