Here is a nice poster to summarize what’s new in .NET Framework 4.5:
http://www.heikniemi.net/hardcoded/2011/10/whats-new-in-net-framework-4-5-poster/
Concerning ASP.NET, I like:
- New site template for ASPNET MVC 4
- Built-in Javascript + CSS combining and minification
- Strongly typed data binding in ASP.NET Web Forms
- Multiple file upload component for ASP.NET Web Forms
- IIS Express used by default (instead of Cassini)