What is a good exploration app?

I do a lot of wild food picking in my city, and I'm looking for an iPhone app that will allow me to save the coordinates of plants that I find so I can go back to them. Something with an interface similar to Geocaching would be preferred - where I can put in specific coordinates (down to the seconds) and it will tell me how far away the plant is, and in what direction. I want the app to be free. The minimum requirement is that it must must must tell me my exact location so that I can at least write it down.

Maps

Any standard GPS app should allow you to do this. If you have an iPhone you can simply tap and hold in maps and it will drop a pin. You can save and name this pin something that relates to the general area. Then, the next time you need blueberries, you could tell siri to "Take me to the nearest blueberries" and it will take you to the nearest location of blueberries.