Loyc.Essentials (nuget): A library of interfaces, extension methods, and small bits of functionality that are useful in almost any software project, according to the theme "things that should be built into the .NET framework, but aren’t".          At least half of Loyc.Essentials is devoted to collections: collection interfaces, collection adapters, collection extension methods (e.g. LinqToLists) and even a couple of collection implementations. The other half includes a variety of things including Symbols, a localization helper, "message sinks", a miniature NUnit clone and more.
Keywords: Loyc|Core|Collections|Extension-Methods|Dictionary|Trees|AList|BList|DList|VList|Cache|Sparse-List|Hash-Trees|Geometry|Math|Utilities|Adapters|Interfaces