MassTransit
A free, open-source distributed application framework for .NET.
4 Alternatives To MassTransit
Amazon SQS
Amazon Simple Queue Service is a fully managed message queuing service.
Celery
Celery helps innovative companies set up pre-order or custom crowdfunding campaigns anywhere.
RabbitMQ
RabbitMQ is an open source message broker software.
ZeroMQ
ZeroMQ is a high-performance asynchronous messaging library.