My son started chores around age 4 too- just picking up, helping 'set' the table with napkins and silverware, etc. Now he does these things:
1) empties the dishwasher and puts away the dishes
2)feeds and waters the dogs, the cats and his guinea pig
3)picks up his room and makes his bed
4)helps me carry the laundry baskets downstairs, and sort laundry, also sometimes helps me fold and puts his own laundry away
5)helps take out the garbage and the recycling and on trash day, helps haul the can out to the curb
6)takes kitchen scraps out to our garden compost pile
7) in summer, helps plant and then weed the garden and pick veggies
8)helps set the table and clear the table for meals
9) helps with walking the dogs
10)helps read grocery list, read ingredient labels and carry in and put away groceries...
wow- he does a lot!! anyway, he earns an allowance now- we get paid every 2 weeks, so he is paid $5 per week or $10 per payday for doing chores willingly and with a good attitude AND doing his homework. If he has a snotty attitude about it or doesn't do his homework, etc. he loses $$. It seems to work really well!