MOSS 2007 and WSS 3.0 SDK's released

The MOSS 2007 SDK includes the WSS 3.0 SDK, so you don't need to download both if you are going to download the MOSS 2007 SDK.

Here are the links:

SharePoint Server 2007 SDK: Software Development Kit and Enterprise Content Management Starter Kit

Windows SharePoint Services 3.0: Software Development Kit (SDK)