We are just beginning to work on a small open source lib for NuGet-powered plugin management called NuPlug. For testing purposes it would be nice to have a little, throw-away NuGet server. Since i am a big fan of vagrant and docker i did a quick search on the docker ecosystem dockerhub finding jonathanmorley/nuget. However, this is just an example of running the NuGet client within docker, not the server.
For a NuGet server, you can simply build your own. But if you want it even simpler, you can use the standalone-branch of TeamCity NuGet support. I hacked together a few files that install and start the standalone NuGet feed on mkoertgen/hello.nuget.server
Hopefully, someone will probably come up with a dockerfile that does just that.