If you commute a lot a good bike rack can be a huge bonus. A backpack or specially designed messenger bag can be great ways to haul stuff around, but it often turns into a sweaty and uncomfortable circumstance. A particularly heavy bag can also cut off circulation to your hands which can be a major discomfort.
There are special panniers you can buy for use with bike racks and plastic buckets can also be used. A guy I ran into this summer modified old kitty litter buckets to fit on his rack. With a drill and a trip to the hardware store, the buckets can be modified to hang from your rack. You can also buy them built to go on the citybikes website.
I decided that I wanted my own “glove compartment” of sorts and a trip to The Container Store inspired me to create this:
I found a rather sturdy box with a lid that was the perfect size. I drilled a few holes it the bottom, screwed it on to the rack with some wing nuts so that I could easily take it off at any time without tools, and a bungee cord ensures the lid stays on tight.
It’s water proof and if you want, it can even be used as a cooler. Simply toss in some ice and whatever needs to be cooled, and you're set. The only thing to be aware of is the “vibration factor.” Whatever you put in such a storage device is going to get shaken up quite a bit. There are ways to dampen the effects. Some loose newspaper for example.