Eagle Creek's Pack-It Specter Tech Clean/Dirty Cube is one of those ideas that's so simple it's genius. Two compartments with a water-resistant divider in the middle allows you to keep clean and dirty clothes separate, so your dirty socks don't contaminate your clean shirts with funky smells or sweaty moisture. It's constructed with an ultralight and tough fabric that packs down small so you can easily stow it at the beginning and end of your trips when everything is either still clean or everything's dirty.