The third SharePoint 2007 book is out now... Microsoft SharePoint: Building Office 2007 Solutions in C# by Scot Hillier. I've got my copy ordered!
Mike Walsh is keeping an up to date list of all the books out now, and coming in the future so keep an eye on his page:
http://www.asaris.de/sites/walsh/Lists/WSSv3%20FAQ/V%20Books.aspx
It's amazing to see the number of SharePoint v3 books coming out compared to v2! Now I've just got to speak to all the publishers to see if I can get free copies to give away at user group meetings! If anyone can sort that out for me drop me an email...