Jay Desai has created an online application which allows users to create and compile Windows phone 7 applications for their smartphone without knowing any code. The software at present mainly works as a RSS, Facebook and Twitter reader, so the use case is limited, but Jay intends to make it work with Youtube, Flickr and other online services, and with enough options it should become a powerful way to rapidly and cheaply make an application to support your website for example. (To give you an idea, we have been told a similar app for WMPoweruser.com would cost $10,000 for example).
Of course the problem then becomes how to get the application on your phone. Unfortunately it mostly comes down to paying the $100 per year development fee to Microsoft, either to submit the application to Marketplace or to side-load the app, something which should help to keep random low-quality apps to the minimum.
See the web app in action here.