I recently found these cycling DIY projects while browsing the MAKE Magazine blog (many of these are from instructables.com):

• Traffic light trigger for your bike shoes
• Make your own aerodynamic helmet
• $30 bicycle cargo trailer
• PVC bicycle repair stand
• Cubicle bike rack
• Bike frame protection
• Make your own carbon fiber/epoxy bike frame

I have no desire to dork up my bike helmet, but there are still quite a few bike-unfriendly traffic lights in the Bay Area. Luckily, I already have some small neodymium magnets arriving soon from United Nuclear that I had no idea how I was going to put to use. Now I just need a bit of epoxy.