Whether you are a road biker or a a mountain biker, there is a GPS that will work well for you. These units can be mounted directly on the handlebars.
If you want somthing for navigating the roads you're riding, you'll probably want a GPS with turn-by-turn navigation.
If you bike in wide open terrain, with little canopy, you might want to consider a Garmin eTrex model like the Legend Cx. If there is a lot of tree canopy where you ride, or if you're in an urban canyon try the Garmin GSPMAP 60Cx, which has the same chipset as the Garmin Edge.
To do turn-by-turn routing you will need Garmin's City Navigator Software.
Mountain bikers may prefer just a data recorder such as the Garmin Edge 205 or Edge 305. If you are looking for better navigation in the open terrain try the Legend CX
