.NET Rest Client Frameworks

Also take a look at the Microsoft.Http client in http://wcf.codeplex.com/ It will be included in future versions of the framework. It is relatively easy to unit test with.

You can also take a look to Spring.Rest client Framework : http://springframework.net/index.html#spring-rest-1.0.0-released

There is also RestSharp. I've inherited it on some projects and haven't fully explored it myself, so I'm afraid I cannot say if it meets your requirements.

The developer of RestSharp is active in the .Net community, so if the published documentation doesn't cover something I would say there is a good chance of getting some assistance.

I have just submitted a patch for the aforementioned problem with mocking file uploads using Hammock and has been accepted into the trunk. See issue 13 for more details.