Commercially I am a C# developer. I love C#. C# is a great strongly typed language. With Resharper installed I can build my ideas in code rapidly and flex it to my will.
When I go home each evening I use Ruby. Even though I have no refactoring support (snif.) I find I am much more productive in Ruby than in C#.
I worked writing a large ASP.Net application for a couple of years. We implemented MVC to try to detangle the view from the model. It always felt like I was fighting the framework, not working with it. The latest .Net frameworks for doing web application are based on Rails... just a couple of years behind. I love the language. I love the CLR. I'm not too keen on .Net.
I find the ruby community to be friendly and vibrant. The rails open source community produces loads of tutorials and plugins that make getting up to speed easy and putting your application together simple.
Another thing to consider (as far as choosing a language to learn) is that ruby is an Object Oriented language. Even classes are objects. C# is a Class Oriented language, ie. it provides you one way to create objects.. define a class first. (not totally true.. you can generate assemblies in memory using codedom.. but that is by no means easy).
This may seem like a subtle point, but there is a difference.. and until you get experience with an OO language like ruby or smalltalk it's not obvious what that is. Once you have felt the freedom of building objects by mixing in functionality at runtime etc. you find that all the 'work-around's you had to do in C# disappear. Not having the safety net of interfaces does seems scary at first.
In all, I'd learn ruby..
- If you are new to programming (totally) I'd start with http://pine.fm/LearnToProgram/
- Then I would learn BDD (RSpec) and get test infected as soon as possible.
- Then I'd consume rails tutorials and screen casts until my eyes popped
The only problem is .. if you start with ruby then later go to C# you'll find yourself going "Aaaaagh! This would be so much easier to do in ruby" all the time. I know I do.