In case you missed it, there is a Hackathon that is going on right now (the submission deadline is tomorrow so you still have time to throw a quick mobile project together).

As part of the Hackathon event in St. Louis last week I gave a brief presentation on how to quickly and easily add a RESTful JSON webservice to your modules, or even create a simple module to do this yourself. I have the source code for this presentation on Codeplex under the dnnweb project, http://dnnweb.codeplex.com/