I always used my backpack and tank bag when I rode 3 years without a car in San Diego. I also had a TimBuk2 hidden backpack in my tank bag in case I unexpectedly needed more room. every now and then I threw a big bag of cat litter or dog food in my jacket and once I wore tires around my waist.
I strapped bike stands, body parts, rims, etc when doing the whole tech-day thing. You can usually make it work!