Useful C# resources

A collection of useful resources to help you master C#

Blogs

The official .NET blog has lots of interesting C# articles, ranging from beginner to expert difficulty.
Scott Hanselman's blog is an active, well written blog on a wide variety of C# and .NET related subjects.
Eric Lippert's Fabulous adventures in coding is a brilliant C# blog, although his subjects are usually quite advanced.
The C#/.NET Little Wonders slides by James Michael Hare on less known C# features.
The C#/.NET Little Pitfalls slides by James Michael Hare on avoiding C# misassumptions.

StackOverflow can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.
/r/csharp is the C# subreddit.
@dotnet is the official .NET Twitter account.
Gitter is the C# Gitter room, go here to get support and ask questions related to the C# track.

In On .NET, Bertrand Le Roy interviews people on a wide variety of C#/.NET related subjects.
There are several great C# courses on PluralSight. The downside: PluralSight is a paid service, but you can request a free trial.