C# is the lingua franca of .NET so you would be best off studying that first. It's still a simple language, especially if you know C++. I recommend "Pro Visual C++ 2005 for C# Developers" (it maps C# concepts to C++ but you can go the other way), "The C# Programming Language 4th Edition (with annotations)" and "C# in Depth". Then, of course, just solving problems with the language.

Next you want to get the latest edition of "CLR via C#" to get a very in depth look at how the CLR works.

Once you're comfortable with C# and the CLR, you can pretty much figure out how the major frameworks must work. For instance, you can understand about 90% of ASP.NET just by learning two classes and two simple interfaces.

Some other good online resources are:

http://stackoverflow.com/questions/9033/hidden-features-of-c

http://stackoverflow.com/users/88656/eric-lippert

http://stackoverflow.com/users/22656/jon-skeet

https://msmvps.com/blogs/jon_skeet/

http://blogs.msdn.com/b/ericlippert/

Oh, if you really want to accelerate your C# learning, try writing code without using `if`, `while`, `for`, `switch` and `goto` (obviously).