Started playing with Go this weekend, and I'm already sure that this language is going to become a keystone in my work. What I like: strong typing with type inference, built-in concurrency, garbage-collection, native compilation across lots of machines, and it's fast. And most of all, it's a very straight-forward, practical language. Oh, and the ability to return multiple values from a function is great. And switch statements that don't automatically fall through. Things I'll enjoy playing with: slices over arrays, defer/panic/recover, channels/select, and the type switch construction (which I'm really enjoying in XQuery/MarkLogic). While I'm looking forward to it, it will be a bit odd for me to get serious with a non-object-oriented language again. It's been years since I've done anything significant with C. But the interface mechanism should help ease the transition.
Now for my first project. Maybe I'll run through the Matasano Crypto Challenges. That's something I've been meaning to do but never seem to make the time.