I recently was sent a link to this free download from the Microsoft web site - a PDF book "7 Development Projects for Microsoft Office SharePoint Server 2007 and Windows SharePoint Services Version 3.0". Phew - a bit of a mouthful!
We gave this book away in printed form to delegates at TehcEd in the USA, and it will evolve into a fully fledged book when Office 2007 is released. In the meantime, you can enjoy it as a free download.
However, I should point out one thing - it uses Adobe's Digital Rights Management (DRM) to prevent you from printing or copying the text, so you have to view it electronically. I'm not sure why they have done this. DRM is a tricky area. User's want as much control and flexibility as possible, and content producers want to protect their IP and copyright. In this case, as some of the material is available on MSDN, and the chapters are really stand alone articles, I'm not sure why they have done this. There are times when I would want to print an article out and read it away from my computer. A colleague of mines tried to get one of the samples working, and had to sit and and retype all the code by hand, as he couldn't cut and paste it - madness!