Top 20 NuGet collections Packages

Provides the ability to List items in Concurrent manner.
New collections and extension methods for existing interfaces like IEnumerable<T> and ICollection<T>
Provides abstractions used as part of adding pagination support to LINQ.
Provides extension methods to augment LINQ-to-Objects with pagination.
Provides extension methods to augment LINQ-to-Objects with additional functionality and patterns.
Provides various .NET collection extensions
Immutable hash collections
A fast implementation of topological sorting that supports stable sorting as well as breaking ties via ThenBy[Descending]
Common C# extensions
F# bindings for System.Collections.Immutable
.NET library that implements an ordered dictionary. Provides all the functionality of Dictionary<TKey, TValue> but also maintains the items in an ordered list. Items can be added, removed and accessed by key or index. Implements IDictionary.
A collection that supports thread-safe append-only writes and lock-free random access reads.
Component containers
NuniToolbox is a collection of common functions for the lazy programmer
Extra methods for dotnet standard library. Similar to Apache Commons Lang for java.
A library that provides reactive implementations of common data structures
Provides a set of features making it possible to emulate C++ Variants for dotnet.