So the next version of Visual Studio is getting ready to release (it is actually already available for download from MSDN), take a look at ScottGu's blog posting or Somaseger's blog posting about its upcoming release.
So what about sos.dll?
Well, before we get into that, there is a little bit more details that we need to discuss. First, what is the difference between the CLR (Common Language Runtime) and the .NET Framework? This is described very well in this post so I won't go into it here other then to say that they are different and it is important to note for the .NET Framework 3.5 release.
Having said all that, so where does this put sos.dll? Well, if you look in the %Windows%\Microsoft.NET\Framework\v3.5 directory, you will not find an sos.dll. Same in the v3.0 folder. This is because, according to Dave's post, 3.0 and 3.5 are both using 2.0 SP1 as their CLR version and since sos.dll is tied to the CLR version, that is where you look to find it. Note that this means you can still use ".loadby sos mscorwks" in the debugger as mscorwks.dll is also being loaded out of the v2.0 folder.
There have been a lot of different things happening with .NET Web Products. For a good collection of the different things available or coming soon, check out this post from Scott.
I'm looking forward to all that .NET 3.5 has to offer us in this upcoming release and I'm excited to work with it more.