Has anyone found GPS software like Tom Tom that costs less than buying a standalone all-in-one GPS unit? For example, I see that the Tom Tom software goes for $150 or more yet buying a Tom Tom One is less than $150 at many places. There are also cheaper units like the Navigon 2100 that go for $100 or less.
With a separate device, you'd have to carry another thing around. But, it has a bigger screen and better (more sensitive) GPS receiver.
As for the original question, you can try
Earth Comber. It lets you download maps for use offline. I've only tried the PalmOS version. It was slow and did not have a navigation function though.