I have one of these:
Puddle Jumper bag on the O List!
I find the shoe compartment is big enough for a pair of VFFs plus some flip-flops for the shower, and it has several external and internal pockets for organizing stuff. I use it for the gym and sometimes for travel (although I like flying with a backpack better). It's stood up well for about 6 years now.
Oh, and I had mine before Oprah put it on her list :P