Useful additions to the .NET Framework and:

• Reactive Extensions

• Fill gaps in existing libraries and provide other useful utilities that compliment core functionality, not provide abstractions or alternative APIs.

• Get equivalent features added to the existing libraries. Though, we understand the likelyhood of that happening for many of the features is low (especially the global ones).

• akarnokd's Reactive Extensions - More reactive extensions
• AsyncEx - A helper library for async/await
• Enums.NET - Like Enum, but better (Rejected Runtime Proposal)
• Humanizer - String formatting done right
• Interactive Extensions - Familiar "reactive extensions" for IEnumerable
• MoreLINQ - All the LINQ you could ask for
• MoreRx - More reactive extensions
• NodaTime - A better date and time API
• Rxx - More reactive extensions (Outdated)

We'll only consider contributions in the spirit of the goals (e.g. the feature fills gaps in an existing library and could be considered useful to a large portion of people).

1. Open PowerShell
2. Run ./build from the root repository path

• StackOverflow contributors

• Jon Skeet for his abundant knowledge and contributions from MiscUtil and C# in Depth