Building a Web 2.0 Portal with ASP.NET 3.5 This is not an app, but a solid book that I am working through right now. It teaches using the most current .NET technology and covers a lot of various subjects within the ASP.NET development "quiver" including AJAX. It is written by the CTO and co-founder of www.PageFlakes.com and pretty much shows you how to build a similar basic Web 2.0 type portal. Some subjects are covered more deeply than others, but it is at least a good primer/intro on all of the subjects it touches. Having used .NET since the beginning in 2002 and old ASP before that, I am finding I still have a lot to learn (and re-learn). Hope that helps.