I found myself thinking about a plugin architecture for a web application, using that hot deploy feature.
I'm pretty sure you already done enough research concerning hot deploy based on the local file system. So here's what I started thinking about: imagine that you instead register with the web application a remote location, where you can get a certain plugin.
You could then use a special class loader to load the remote plugin and incorporate it into runtime. Wouldn't that be great? You could even do some pretty neat stuff, such as dependency checking, remote dependency resolution... Even obtaining a plugin directly from CVS/SVN and compile it into runtime!

And a simple low priority thread could check for the availability of updates, and present the results to any administrator logged in.

What do you think about this?