Where can I find replacement screws? I have a handful of rusty screws on my bike; where can I find such small parts?
Most bike screws are 4, 5, or 6 mm allen bolts. Any bike shop will also have these in stock. You could probably hunt up some stuff in your local hardware store, just bring your bike along. 

On the net:


Loose Screws bicycle small parts
Planet Bike does free shipping on small parts (scroll down a bit to rack hardware and such)