My husband is out of town for the week and I have been getting groceries for me and the kids without using the car. Anyone can use their bike trailer to get groceries, but the trick is that I have been using it to get groceries while hauling the little ones (ages two and three) along with me. The elderly Burley trailer has enough room for a few bags and since there are stores so conveniently located, we've just been popping in often. We also went to Goodwill today on the bike to pick up a few "needed" items, thus maximizing our savings!
In fact, the only place we've been by car is their drop-in day care. In the interest of full disclosure, I did pick up something at the store in that same shopping center, but I did not move my car in between, so I think it still counts as not using the car.