my partner and I use a Bikes at Work 32" trailer for our groceries and other provisions. We cook all our meals, and buy wine by the case, and have three cats, three chickens, and an active garden, so we tend to pile on the goods when we make a run.

This trailer was THE piece of equipment that finally allowed us to get rid of our car. We've used it for most of our big shopping since we got it in 2002. It's an aluminum frame that is designed to carry two 18gal Rubbermaid containers.

Ours is the smallest one made by BAW, yet it's pretty big, and heavy, compared to all of the other ones we looked at. It offers a 300lb capacity and handles very well, especially when loaded. It requires a large rear wheel (i.e. an MTB XC wheel) to safely pull a very heavy load, but 700c wheels work for <100lb loads. We have a hitch on each of our cargo bikes so we can take turns being the Beast of Burden.

It's also handy for carrying bicycles (disassembled), folding bicycles, and the luggage of visiting friends when I go to pick them up/ drop them off at the train station.

edit: www.bikesatwork.com