what bag for commuting - running erands?

[bean fidhleir]

I used my very capacious backpack for shopping, at first. But I found it was too good at turning my back into a lake, so I bought a Topeak wire basket that clipped to the top of the Topeak rear rack. But loading that basket up made the center of gravity unpleasantly high, so I switched to Nashbar fold-flat grocery panniers which have been very satisfactory, and will no doubt be even moreso when I finally modify the rack with a new crossbar/mounting point and shift them down.