Diving deeper into C# - Suggestions please

I would consider myself an intermediate C# programmer because I know the basics of the language well, optimizations to make for clean/robust code, and how the CLR/JIT works. But I haven't really went outside the realm of creating stand-alone applications. What I'm asking for is suggestions to add to my research in learning C# and programming.

I'd like to start looking at network programming, database manipulation, and some other common uses for C# in the business-software world.

All help is appreciated :)