We've been seeing an increased demand for info on 64-bit programming. This site has a bunch of links to related 64-bit content (articles, SDK, multimedia)
Intro to Developing Apps for the 64-bit Itanium based version of Windows
Windows Data Alignment on 64-bit IBF, x86, and x86-64
Platform SDK: Introducing 64-bit Windows
Route 64 - Kang Su Gatlin talks about 64-bit
The .NET Show: Getting Ready For Win64
Hope this help!
Updated with additional link: http://msdn.microsoft.com/netframework/programming/64bit/