If you haven't done so already, join Code Eval https://www.codeeval.com
it's a great way to brush up or learn a new language. There are challenges which can be solved using the language of your choice. Its kind of like a game, you earn points and get ranked. There are sponsored challenges and potential for finding jobs. When you do this, find me "philn5d".
There's another site called Top Coder with challenges. This one has payouts for sponsored challenges, but also pure algo challenges. The sponsored challenges are companies paying to have some work POCd or perhaps actual implementations. Given that, the payouts are actually really low considering what they would pay a contractor and you'd have to place top 2 or 3 for a payout. But, there are really interesting challenges, most of which are technology constrained. Give it a try, you may like it and may earn a few dollars in the meantime it is free to join. http://www.topcoder.com/
I'm on there too.