"Developers typically see a tenfold productivity increase when they switch to Python" according to Bruce Eckel, speaking during a Design Patterns In Python class.

Check out Bruce's Thinking in Java. I bought the printed version of this after going through the first couple of chapters of the soft version. Highly recommended.

Thinking in Python is an interesting project. It isn't a Python tutorial - it's mainly about patterns, with implementations in Python.

If I were interested in C#, I'd take a look at Thinking in C#, a preliminary version of which is now available. But I'm not, so I won't.