That's pretty trivial to do with nginx though, isn't it? I have a server that can run php on certain subdomains AND folders, node.js on others and I suppose ruby would be pretty easy too.
In fact, on one domain nginx sends part of the traffice /static/ directly to that actual directory, and anything else gets picked up by node.js.
Or is what I'm doing really stupid? I'm not currently running anything significant on my servers, and this is not my primary domain of interest, so I've never checked how risky my setup is. Maybe you could tell me if that's the case?