Visual Studio 2010 Service Pack 1 is now available on MS Downloads.

You can see the full readme here, and read about it in detail on the VC Blog.

The Service pack includes a number of fixes, particularly for some problems with the X64 optimizer.

Update: If you are looking for them, the locations of the Visual Studio 2010 C++ Redistributable packages for the Service Pack 1 version of the CRT can be found here.