Carry shopping bag
Carry items downstairs or upstairs to a specific location
Carry mail or newspaper into the house
Send the dog to get an item from another person/return with it
Carry items following owner
Pay for purchases in shops at high counters
Transfer items from a shop assistant to a wheelchair user's lap
The list is by no means exhaustive, there are many many more tasks a dog could do ... if you can think of it ... then you could probably teach it!