Both the WSS v3 and MOSS 2007 SDKs have been updated again. You can get the latest and greatest CHM's from MSFT downloads. The download includes both the WSS and MOSS SDK CHM files for offline viewing. Check the download page (linked below) for a list of all the new and updated stuff in the SDK.
There's also a new addition to the download: the BDC Application Definition Editor Tool. While not as full featured as the commercial BDC Meta Man product, it is something that makes the lives of BDC developers a little less painful than hand-editing the application definition XML files.