Photo 365 - Everyday Photo Calendar for Your Life is a great iPhone app that I used to inspire me for my Photo 365 project from last year (still going by the way!), and it just received a huge update, with iCloud syncing, bug fixes, iPad and iPhone 5 support, and a host of other fixes.
If you’re interested in improving your photography, a photo-a-day project is a great way to start. You can read about my experiences, or just download the Photo 365 app (or a similar one, should a different one float your boat) and get started today (no need to wait till January 1).