My favorite new app is Marine Traffic. (Actually it's not that new just new for me). Basically it gives you AIS on your iPhone or iPad. So long as you are within range of a cell tower you can get full details of vessels within range.
It's good on the iPhone and awesome on the iPad. Here are some screen shots. Basically, you use the map to see ships in your area, touch the icon to see detailed information about the vessel. It's availble for iPhone and Droid.
