I always cut the legs off of old, worn out jeans and corduroy pants in the summer so I can save money on shorts. I felt wasteful just throwing away the excess fabric, so I decided to do something with it. I needed bar tape for my road bike, so I cut the fabric into strips and sewed it together. You could do this with pretty much any fabric that isn't too thick (tee shirts and flannels would work pretty well), but I'll show you how to do it with a pair of jeans.
-Legs from jeans (or some other fabric)
-Two wine corks
Step 1: Cutting the Fabric
1. Cut the hems off of what's left of the pants. Save these for later if you're really into DIY biking gear!
2. Cut the fabric into strips about 1-2 in. in width. The length doesn't matter very much. Mine were around 15-16" long. You should end up with 16-18 strips, which should wrap 2-3 full handlebars.
Step 2: Sewing
Sew the strips together end to end with your carpet thread. I'd use carpet thread because of its strength and toughness. It only took me about 4 strips of fabric/strip of completed bar tape.
Step 3: Wrapping the Bars
1. This is done in a few different ways. I like to start at the top of the bars instead of the end of the drops, but some people prefer to do it the opposite way. I'll show you my way though. Take some electrical tape, and tape one end of the bar tape to a spot on the top of the bars. Then start wrapping until you get to the end. Take a wine cork or other bar plug, stuff the excess bar tape inside the bars, and plug the bar ends.
2. If you saved the hem from earlier, you can use it as a toe strap for your pedal cages. Just pull it through, trim it where necessary, and tie the ends together.
Now you're finished, free to show off your awesome bar tape to the world! Go ride!