Top 20 NuGet messaging Packages

The reusable package Jeylabs.WindowsMessaging is handles message queing between two applications (exe).
SDK for the LINE Messaging API for C#
AzureServiceBus Transport for Eventfully
Lightweight Reliable Messaging Framework with Outbox
AzureKeyVault KeyProvider for Messaging
Automatic fiber based proxy generation
Lightweight Reliable Messaging Framework with Outbox
Extension to SlimMessageBus that provides Avro serialization based on the AvroConvert library
Extensible chat framework for systems with microservice architecture. Common security rules.
This package helps you to build messaging job on attributes.
A package which will help you to register all DipScope.Messaging.MessageStore.EntityFrameworkCore services in .NET Core application.
A package which will help you to register all DipScope.Messaging.EventStore.EntityFrameworkCore services in .NET Core application.
C2DM/GCM library to send messages to Android phones.
octalforty Mechanic is a nice and simple lighweight embeddable message bus for .NET.
This package includes the community version of WebSync Server 3.5.0.5 plus the code from the WebClient example to get started.
WP7Contrib messaging extensions for MVVM light framework, contains custom implementations of MVVM light messenger classes. Contains the following assemblies: WP7Contrib.Messaging.dll