Actually, we have a reality show called "Shipping Wars" which seems to follow these gig-worker oddball shipping guys. That's a good point, but I am not aware of what sites these guys use to bid on jobs. Nothing is jumping out on Google, but I'm probably using the wrong search terms. I'm not likely to watch the show to do more research...

EDIT: Wikipedia says the reality show takes bids from uShip.com in the first 8 seasons.