Professional DotNetNuke 5: Open Source Web Application Framework for ASP.NET (Wrox Programmer to Programmer)
Be sure to get it when it's out!
DotNetNuke 5 User's Guide: Get Your Website Up and Running (Wrox Programmer to Programmer)
Professional DotNetNuke Module Programming
Done in 60 Minutes: Building a Custom DotNetNuke Membership Provider (Wrox Briefs)
Beginning ASP.NET 3.5: In C# and VB (Programmer to Programmer)
Professional ASP.NET 3.5: In C# and VB (Programmer to Programmer)
DotNetNuke Skinning Tutorial: A simple, clear, step-by-tutorial to creating DotNetNuke skins to put you in control of the look and feel of your DotNetNuke website