Codewars is a fun site with simple programming exercises. The kind of stuff you can do over lunch if you've seen all the let's plays on youtube already. (oh and that here is obviously referral URL I'll be getting worthless internet points for if you use it, what did you think...)
As is fashionable these days, they implemented point system, and even top 100 ranking. Of course inevitable consequence of gamification is that someone is going to write a walkthrough on how to minmax the shit out of it.
By the way you can cheat quite easily by googling answers or creating sockpuppet account, unlocking everything on it (which forfeits eligibility to get points), and copy&pasting answers to your main account, but I'm talking about getting to top 100 legitimately.
There are points for creating your own problems, having forum comments upvoted etc., but that's just way too much work, and it takes forever until it gets approved and you receive points you need, so let's ignore it.
The point system is basically:
- 8/7 kyu - 1 point
- 6/5 kyu - 2 points
- 4/3 kyu - 5 points
- 2/1 kyu - 10 points
- any beta - 2 points extra
How to score high
- Ruby - easy language, ton of Ruby-only katas
- Python - easy language, ton of Python-only katas
- Coffeescript - that's actually important, there's a lot of JS/CS only katas
- Haskell / Clojure - if you're really good at them, it's much harder to half-ass them than with Ruby, Python, or Coffeescript, you don't have IDE or REPL to help you, and they have few katas
- Java/C# - don't even think about it, they take forever, verbosity vomit will spoil your lunch, and they added them recently so there are very few katas for them