Professional K2 [blackpearl]
It's time for a shameless plug...
The end of another project draws near for me. We're finishing up Professional K2 [blackpearl] and it should be out sometime in fall or early winter. The book is now available for pre-order on Amazon and other sites - yes, that's my mug on the far left end. This book isn't only for developers, but also for business users - so if you use K2 blackpearl, or want to use K2 blackpearl, check it out.
If you aren't familar with K2 and you use Windows SharePoint Services (WSS 2.0 or 3.0) or Microsoft Office SharePoint Server (MOSS), Workflow Foundation (WWF), ASP.NET or just plain .NET applications and find yourself struggling to maintain applications that have any variety of workflow/BPM in it - check out K2, it's a pretty awesome product that will make your life about 20 times easier. If you're not familar with K2, the book will give a great introduction and some in-depth coverage as well.
If you need assistance with K2 - call my company, ATGi - we're also K2 Partner's.