There's been a lot of excitement recently in the Open Source community about Ruby on Rails. This web development framework makes developing web applications much easier by providing a well structured Model/View/Controller framework in which to develop.
Of course, having this kind of framework available to ASP.Net would be even more exciting, the MonoRail project was a great find. Part of the wider Castle Project, it provides a true separation of presentation from business logic and persistance of data.
There's a nice database persistance layer as part of the project, too - ActiveRecord. Great for .Net 1.1, but possibly with some issues under .Net 2.0 as it relies on untyped collections. But I've found that there's a good article on implementing nicely typed collections for related objects tho, here, so I'm now less worried about using ActiveRecord as the persistance layer.
I'm going to try implementing a test with this later today, but it looks good from the documentation. There's even a stud for documentation about implementing the Inversion of Control pattern using the Windsor Container within the framework - all very interesting stuff.
Whether I manage to integrate MonoRail with AJAX (maybe using ATLAS) will be the real kicker, of course, but if it can be done, I think this could be an extremely powerful development framework.