Skitch is a screen capture app that allows you to draw on the images. This makes for an amazing real estate tool.
Take a photo of a house and draw on it. Use the built in maps to add areas of interest to a community map.
Once created, the maps sync with your Evernote account. They can also be saved as a photo or emailed.
So quick and easy, it makes the investment in an iPad or Droid tablet worth the price.