I don't think I will have a lot of use for a lot of apps.
I get a lot of use out of the apps I have either bought or use for free:
drop box - put a doc in your folder on your laptop and voila it appears on your phone within seconds. perfect for hotel reservations, airline stuff etc etc
co-pillot live - turn by turn with voice turns your android into a stand alone GPS
easytether pro - connect your laptop anywhere there is a cellular signal and have 3 - 3.5 G or even HSUPA download speeds
Flighttrack - plug in your flight itinerary's and it updates itself if a flight is delayed etc + give gate info which is premium if you are in a very large airport.
Package tracker pro - track your fedex, ups, usps, canadapost packages on the fly easily and accurately
Places on my Motorola Atrix. Damn valuable if you are in a distant city and want a Starbucks! type in latte and it pops up all the local coffee shops. Went off a bit when in the Okanagan last week. I was looking for a certain winery and it did not compute.
Pocket Wallet - load it up with all your passwords etc and has strong encryption.
Those are my top used apps. Plenty more out there too.