.NET 3.5 SP1 GDR is available to download
The General Distribution Release with fixes for .NET 3.5 SP1 is up, albeit a bit late, as downloadable content on Microsoft.com. Note that this is an application compatibility release, and these downloads aren't setup to be friendly to end users.
If you are a developer affected by an issue, you can download these updates. If you aren't affected, I suggest you wait - this is not the way the vast majority of customers will get this fix. Wait until these updates come down via Windows Update next year. As of today, we are still on track for 2009Q1 availability of 3.5 SP1 on Windows Update, and at that point you'll see machines with .NET start updating to .NET 3.5 SP1 with this additional GDR applied.
You can download the packages for the app-compat GDR here. The KB is KB959209 and it should be updated soon with details.
Windows Vista, Windows 2008 Server - x86, x64, IA64
Windows XP, Windows Server 2003 - x86, x64, IA64
I am still on vacation in Africa so I haven't got details yet on registry keys for detection of the GDR, so bear with me. I'll try to get those details ASAP, as well as how to integrate these fixes into your setup if need be.