[LakePirate]

It's called RunKeeper but seems like it would work great for tracking and logging sailing activities. It tracks speed and distance and will show mapping.
And its free. I havent tried it on the boat yet, but it works great jogging.

 

[bossk]

TrailGuru sounds the same or very similar, I use it for jogging. Keeps track of everything with a Google map's display, has all sorts of activity options. It is also free. I like it a lot.