I previously posted about my mishap with the Kleen Wheels PermaCap, a neat gadget (when it works) that replaces the fuel cap on some cars, and allows quick re-fueling without having to bother with unscrewing the fuel cap. It does this by proving a spring loaded door in the center of the fuel cap, which you push in with the fuel nozzle when you want to fill up.
Kleen Wheels sent me a replacement PermaCap, and I have been running with it for about two months. So far, no Check Engine lights, and no evaporative system leak codes.
I am not ready to endorse it, but if you are willing to give it a shot, and it works on your vehicle, it can be a very convenient thing. It is not a bad deal for about $17.