I was rooting around last night during a spot of insomnia when I found this potentially illuminating site,
The Patrick O'Brian Mapping Project. Quite simply, it shows the routes of all the voyages taken by Jack Aubrey in his adventures, book by book.
I have a decentish sense of geography, but I already can tell that this site will help me be much better grounded as I follow the course of Jack's travels. I hope some others find this fun, also.