[jackowayed]

Phusion Passenger 3 is going to have a feature similar to that: http://blog.phusion.nl/2010/07/01/the-road-to-passenger-3-te...

>Imagine having a directory full of Ruby web apps, e.g. ~/Sites. To deploy an app, just drop your application’s directory into ~/Sites. To undeploy it, remove the application’s directory. The application directory’s name is used as the domain name. No manually signaling the web server for a restart.

[cmelbye]

While that sounds very useful, what I'm working on is more along the lines of Heroku's distributed dyno model. In their terminology, a dyno is a Thin web application server process. When an app needs to be started up, it will be possible to determine how many dynos are needed, and they will be automatically started up across the grid of virtual servers and balanced using a custom load balancer.