Cycling enthusiast and maker OddJob has created the "BAR T.A.B.," a "take along bar" mounted to the inside of a bicycle frame. It's basically all our favorite things in one simple project.
The process includes building a simple skeletal frame that mounts to the bike's top tube. A back wall is attached, and a set of dividers and shelves are installed to keep the goods. The front door is the same as the back, but attached with a hinge that allows it to open, becoming the "bar" itself. It's supported on the right pedal and crank with a simple spring clamp.
Get the full tutorial from OddJob at Instructables: BAR T.A.B. (Take Along Bar)