For the bike riders who have to dress formally, the commuter Suit from Parker Dusseau is a godsend. The suit is made to be breathable and even features zippered vents for when you're about to break a steady sweat. The fabric stretches to allow for a more comfortable riding experience and the pants sport a button cuff so you can roll them up easily and keep them from the devilish jaws of your chain.
On top off all the other features, the shirt, pants and other accessories even have reflective elements that can be hidden during the work day to help you out on your ride home after the sun goes down. Available online.