Mobile Tide Charts
Of the tide chart apps I have tried this is by far the best. It uses Google Maps to help you focus in on your desired location and allows you to save favorites for easy reference.
This is a necessary download for any lobster pirate who doesn't rely on a hookah, and still actually cares when slack tide is. Check it out at http://www.bluefinengineering.com/. There is also an ad-free version for $1.99.