Awesome capistrano resource:
Capistrano Get Servers
What about rubber gem? It doesn't suit you well?
I'm truly pretty new on Ruby, but this was developed by a friend of mine and he uses chef for boostraping the servers and capistrano strictly for deployment, there is when he came with the idea of the getservers above. In our case, the rubber gem wouldn't work, but it is a nice alternative as well.