Bike handlebar bags are freakin' awesome tools. They can strap to your handlebar bags and carry your things as you ride. They can be anywhere from a small bag to hold just a few things, to a larger bag used for bicycle touring.
Here's a new video of one of our smaller waterproof bike handlebar bags which can be used to carry your cell phone, wallet, keys, bike tubes, a change of shirt, bike tools, or more. This little thing "The Burrito Handlebar Bag" is very light, is waterproof, and great for bike commuters. It can roll up and be placed into your backpack or pocket when it's not in use.