Not officially launched yet, but if you search for likely keywords (try ‘photo’) in iTunes Music Store, your results might include some applications.
Click through to “see all” and you’ll be presented with a heap of apps you can download and install – yay! I’ve only been getting the free ones, but there’s loads in there to buy also and not stupidly priced either – I think this is going to be a hit. How do Apple keep pulling this stuff off?