An update of what I have found lately
GPS Drive - a very cheap and decent turn by turn navigation package for driving or walking
Eye Glasses - this is only for the 3GS (better camera) but works like a magnifying glass. Great for those tiny print menus or back labels
Zagat - if you are in to Zagat, this is a nice front end
RedLaser - does a decent job of reading bar codes and telling you what the product is and where else you might buy it.