Google Android i-jetty
i-jetty is a port of jetty that can run on Android powered mobile devices. This gives you yet another way to extend your handset's functionality. Without i-jetty you must download applications specially written, compiled and packaged for the Android platform. With i-jetty, you can dynamically download plain old webapps that have been written against nothing more than the servlet specification. You will need to convert the java classes for your webapps into Android format, but the Android SDK comes with the tools that you need to do that and i-jetty also ships with 3 sample webapps to show you how to get started.
One i-jetty webapp in the distribution, the Console webapp, demonstrates the power of having a web server on your mobile device: with it you can bridge between the Android environment and your favourite desktop or other mobile device browser.The Console webapp allows you to access and manage on-phone data such as your contacts, address books, music and images handset from any off-phone browser.
The i-jetty project is hosted at Google Code, so check there for sources, documentation and downloads. i-jetty can also be downloaded directly onto a handset from the Android Marketplace.