Okay here\'s my problem. I type in \"rails s\" and then my terminal won\'t let me type in any commands. So I have to start a new terminal window, which is pretty annoying. <
I don't believe there is a way to do the thing you are specifically asking for.
However, I use Iterm2 which allows me to open multiple terminal windows in one window, either by splitting my iTerm2 window or by creating multiple tabs. That way I can just make the terminals that are holding rails server and my development.log tail very small unless something interesting happens in them.