After years of commuting quite a few items, many useful:

Have been using for several few years

Cuisinart food processor - didn't look used much, labels still on blades.
Vacuum cleaner
Inverter - so I can plug household electrical items into car
step ladder (lots of clearance from passing traffic when riding with 4' ladder across back of bike).

Raspberries, occasionally blackberries or blueberries

Other items
bicycle frame (Reynolds 531 frame)
Tools (primarily pliers, screwdrivers)
Other bicycles being discarded by neighbors

Lots of bungee cords; most useful when I needed an extra cord for the ride home