For some reason searching for .Net 4.5 on Google brings up the link to the .NET 4.5 Release Candidate download, when the final is available.
You can grab it here: http://www.microsoft.com/en-us/download/details.aspx?id=30653
(I seem to recall this happening back when .NET 4 was released – you would think MS would put a big note that the Final is out, but instead I found it in the “What other’s are downloading” below.
While you’re at it, check out the new features: http://msdn.microsoft.com/en-us/library/ms171868.aspx
Probably my favorite new functionality is the async / await pattern for asynchronous coding. It is so ridiculously much better than the delegate / callback pattern you have NO idea. Seriously, we’re talking an order of magnitude reduction in code complexity.