I have a rack with a pair of soft nylon saddlebags hanging pannier-style on the sides. Each bag is big enough to hold my large bulky round skater helmet if nothing else is in there.
I'd like to get proper rear pannier baskets, or a basket that could mount on top of the rear rack while the saddlebags are there. And a front basket for things that I want to keep an eye on when I'm riding.