Downloaded Navfree for the iPhone last night. Uses open street maps for data, is absolutely free and looks great but the the routing is a little off at the moment.
Used it for a trip from Chester to Northampton (and back) this morning and it decided to take me through northampton city centre which tomtom doesn’t do so it’s not quite right yet. But the developers are updating it regularly and it looks like it could be a great app.
Oh yeah…… available for Android as well.

Yep. Not bad for free eh?

I find that skobbler (also based on OSM data) does a better job of routing, but the Nav Free interface is much better and the voice is less grating.

The OSM mapping is less than perfect in some areas, but you can always get along to http://www.openstreetmap.org/ and fix any issues in your area. (I’ve filled in some fairly large areas of Newcastle).

Try also BikeHub and CycleStreets for bike based mapping using OpenCycleMap.