There are some sweet options out there for adding a trunk to your bike, but if you're looking to save some cash or just feeling inventive, try this alternative from Instructables. Using a plastic toolbox as the foundation gives you a cheap, durable starting point, and lets you create different trunks for different purposes:
A small weekend trunk for fun rides
A larger commuter trunk with room for a change of clothes.
A "Good Samaritan" trunk, with a set of tools for helping other cyclists in a group ride.
As bicycles become more popular this year, the five-finger supply chain is working hard to keep their "inventory" fully stocked. If you're a daily commuter, you're that much more exposed, especially if you commute to a location in the city.
They say that no lock is truly theft-proof, but that's not really the point. Your locking set-up simply has to be more difficult than the next guy's. Thieves don't enjoy working hard, and will walk right past your Fort-Knox'ed Bianchi to grab that Schwinn with the Walmart cable.
So for the ultimate in visual and physical deterrents, try this: Grab a couple of these Master Lock U-Locks and cable-tie the U and lock portions together. Set the combinations to match as well. The result: the thief now has two locks to cut, while sparing you some of the annoyance of fumbling with two separate locks.
The design of this particular U-lock makes this easy, because the combination numbers are on the bottom of the cylinder, so they'll be right next to each other when you're ready to get going.
and cable-tie the U and lock portions together. Set the combinations to match as well. The result: the thief now has two locks to cut, while sparing you some of the annoyance of fumbling with two separate locks.