Updated (2017): See .NET Framework Releases to learn about newer releases.
As previously announced, starting January 12, 2016 Microsoft will no longer provide security updates, technical support or hotfixes for .NET 4, 4.5, and 4.5.1 frameworks. All other framework versions, including 3.5, 4.5.2, 4.6 and 4.6.1, will be supported for the ...