The Salesforce Mobile Developer Challenge 2013 is live. I'm pretty excited to see the entries that folks come up with this year. You have until June 3 to finish your applications so you have a few weeks to get moving. There are a number of Mobile Packs that you can use to get started rapidly building applications.
I have started on my entry last weekend. Once I submit my application on June 3rd I'll post my GitHub Repo and the YouTube video on this entry so folks can see what I built and how.