Has everyone seen Advent of Code?
It's a site with a series of programming problems that are being revealed one a day, a la an advent calendar. You can read more about it here.
I came to the party a little late so I'm only up to day 6.
Each problem comes in two parts. The second is revealed after you complete the first. Both students and teachers are enjoying the problems.
What I like about the Advent of code, besides the one a day release, is the fact that at least so far, the problems aren't super crazy hard. They require a little thought but they seem very doable.
For me, that makes them a perfect platform on which to play with a new language. I'm working through these in Clojure. I've been putting my solutions up here. I have no idea if my code is "good" Clojure but it's been fun nonetheless.
So, if you're looking for a nice set of small programming problems and want to explore something new, check it out.