The following resources contain additional information about parallel programming in .NET:
The Patterns for Parallel Programming: Understanding and Applying Parallel Patterns with the .NET Framework 4 document describes common parallel patterns and best practices for developing parallel components utilizing those patterns.
The Design Patterns for Decomposition and Coordination on Multicore Architectures book describes patterns for parallel programming that use the parallel programming support introduced in the .NET Framework 4.
The Parallel Programming with .NET blog contains many in-depth articles about parallel programming in .NET.
The Samples for Parallel Programming with the .NET Core & .NET Standard page contains many samples that demonstrate intermediate and advanced parallel programming techniques.