Okay, I'm a total lightweight compared to the rest of you. Instead of panniers, I carry one of these http://nymag.com/shopping/bestbets/wednesday/29372/ which I keep in my handlebar bag. I take it into the store, fill it up, then when I get on the bike, I hook one strap over each shoulder and use it like a backpack. It doesn't hold that much, so if I need more stuff, I make another trip (I like the added miles ). I shop daily, so a second trip is pretty rare. Just a simple alternative to a fully loaded trip, and really fun, too.