Google's App Engine
We've got a talk at our university about App Engine by Googler Mano Marks. In short App Engine is Google's alternative to LAMP. And, like Gmail, Google is offering you free hosting for your web-based application (up to certain storage and daily bandwith limits).
Application logic is written in Python, although other languages might be supported in the future. And backend storage is based on BigTable, which does not follow the classic relational model of many *SQL databases. For me these are two changes that may turn some developers down, but the strong point I think is that developers can forget about scalability or availability problems.
While I've created an account and I've downloaded the SDK, I'm only studying the demos at the moment. If you are interested on learning more I think you'll find the video from Developer Day interesting.