MSDN has the latest SDKs for both MOSS and WSS and these are also available for download. Nothing new for Project, and I am not aware of any planned releases of another SDK - but do please let me know if there are some samples you really need and we can see how we can best get these to you.
Full details of the latest and greatest for SharePoint can be found on Randall's blog or to go direct to the downloads here are the links:-
Don't forget that the Windows SharePoint Services 3.0 Tools: Visual Studio 2008 Extensions, Version 1.2 were also updated recently and now work with Visual Studio 2008. Download them here. The extensions can only be loaded on x86 architecture (I missed the note, so I will repeat it here).
Note: This download does not work with an x64 OS. We currently recommend a x86 development machine for SharePoint development when targeting x64 OS for test and production. Output binaries are all .NET assemblies so you can reasonably expect all .NET assemblies built on the x86 dev box to still work on your x86 OS test and production machines. The CLR will JIT compile the .NET assembly on each target machine and will optimize for x64 OS when run on that architecture. Testing on x64 after doing development on x86 is still recommended.
And if like me you have x64 operating systems on all your x64 servers - then look to Hyper-V and host an x86 Windows Server 2008 for your development!