As a programmer, do you work on home projects? As a designer, do you doodle design ideas or make puzzles? As an artist, do you do portrait work?

Having hired many people in the past, one of the things I can speak to with authority is that those people who spend their off time working on discipline-related projects are the ones who are always up on current trends, have new ideas, are most willing to try something new, and will be the ones taking stuff home to tinker with on their own time. Now that shouldn't be expected of everyone, but the sad reality is that there is competition for jobs out there, and those who are prepared to put in the extra work are the ones that are going to be in hot demand.

Demonstrating that you learned C# over a weekend because you thought it was cool for prototyping is exactly the kind of thing a programming manager wants to hear. Suddenly your toolset expanded, and not only did it show willingness to do something without being told, it makes you more valuable.