A few months ago, I made a set of panniers for my bike out of some cheap canvas at Hobby Lobby. They were my first major sewing project, so I put a few things together in the wrong order. I left the clips off until the end, the straps were spaced wider than I'd have liked, and a few other things weren't quite right.
Even so, they came out very well. My old panniers barely fit a 10# flour bag, and failed under the load. These are large enough to hold twice that, and would barely notice the weight. They can roll up and clip out of the way, and they look slick (They're unadorned black; my absolute favorite color scheme.)
I decided to make another pair for my girlfriend, and took my additional experience into consideration. The second pair was easier to make and came out incredibly.