I recently worked in a Rails project with Peter (@sporkd). The project is intended to be used as a sub-site, and should be served under sub-URI. After google, we ended up by setting config.assets.prefix and wrapped all routes in scope. The solution is simple and worked well. But soon, some weird bugs were found, and Peter was successfully isolated the problem to session (see demo sporkd/asset_prefix_test).

The web application landscape has changed drastically in the past year or two. Where once every site was a silo unto itself and could reasonably expect users to create a unique login and password for each site, it is now a different story. I sigh every time I have to fill out yet another registration form, wishing instead for a simple "Connect with Facebook", "Sign in with Twitter", or "Log in with OpenID". At the same time, services are more interconnected than ever. One of the best ways to increase the popularity and viability of a new service is by piggybacking it onto the existing user bases of apps such as Twitter, Facebook, and Foursquare.