Earlier this year I started working with .NET, C# specifically. Since then I have also started to jump on the Ruby bandwagon. Most recently I've gone back in time and started re-learning C++. It's enjoyable spending time and getting into each language. I think it is valuable to have an understanding of what else is out there. Without a doubt I can see how expanding my knowledge with these languages will benefit me in general. I find that opening my mind to different concepts helps me with me think of things like: "How can I do something similar to this in Java?", or "What is the equivalent syntax for this in C#."
Next steps Ruby on Rails... or maybe I'll have to break out my old SmallTalk books.