I've been working on a project for some time now, the Turk Framework, that allows you to interface devices and applications to web apps by writing simple driver scripts.
The idea is that you can write a simple python/ruby/etc. script that talks to your device or application, then use a template to create a simple web application (which we'll be able to host online for free), and when you log in, you'll get web interfaces to control all the connected devices. It uses XMPP to push data down, so everything is real-time.
We've mostly been focusing on controlling wireless devices (zigbee, bluetooth, wi-fi), but I was wondering how many people would be interested in using this to control an Arduino-based project connected directly to their computer. There could be a bunch of included libraries for common protocols like Firmata, plain text, midi, etc. and all you'd have to do for most applications is run a basic pre-made driver. Then if you went to the app and selected the right serial port, you'd have a basic web interface accessible all over the world. You could also automatically update the firmware on your device through the web interface.
Anyone interested? I'm open to suggestions, so if you want to use this for a project sometime soon or have more ideas, fire away!
http://github.com/robbles/Turk-Core - still a work in progress