To see even more handy tricks, check out the rest of the saga at
Handy Tricks 9: Oodles of random tricks
and Handy Tricks 8: Island Handy Tricks
and Fifty Handy Tricks.
and 40 More Handy Tricks
and Australian Handy Tricks
and Guatemalan Handy Tricks
and Yet More Handy Tricks
and Handy Tricks Six!
For a bunch of things that didn't work, check out How Not To.
First trick: Improvised Freewheel Removal Wrench
Every brand of freewheel has a different pattern of grooves inside it. If you don't have the right wrench you usually can't take it apart. Unless you can improvise one. This method works well for the most common shimano freewheels.
Remove the axle from the wheel.
Insert the biggest hex wrench you can find into the freewheel. Pound some nails or a big staple as seen here into the grooves to lock the wrench in place. Unscrew the freewheel. Wiggle the nails out.
To learn about why you'd use this tool, what the real one looks like, and everything else about bicycle mechanics, look at Sheldon Brown's site and Park Tool.
Step 1: Chain Whips
To make a chain whip, use your "chain breaker" tool to take a chain apart making two pieces of chain with as many links as seen here. Then drill three holes in a piece of steel bar and grind a curved divot where the short chunk of chain rests. Use the chain breaker to attach the chunks of chain to the steel bar, and you're in business. If your breaker doesn't reach to attach the chains to your wrench, just pound the pins in place with a hammer.
You probably don't need two of these, but it's easier that way and they're quick to make.