Hall of Fame
There are some well polished, shiny applications out there that do what they should and are reliable for actually using them, not only playing with them.
If you think an application should be added to this list, please open a thread on the om-community mailinglist first to discuss the app so that this list's quality stays high. (At least my opinion. Tanuva)
Displays Openstreetmap.org maps
You know that game where you have a metal ball on a tiltable wooden board and have to get it to the finish avoiding holes? Here you are. Addictive!