Copilot for SatNav (but Google Navigator does the trick)
Google Earth/Maps for general mooching/searches
Cardiotrainer for ride tracking
OruxMaps for tons of different layers included the OS maps.
I use Cyclemeter on my iPhone - uses GPS for mapping, gives you all sorts of useful info about speed, distance etc. and once you save a route you can compare rides. I think the newest update can connect to certain cadence meters etc. Not bad for £3 IMO