I got the idea for this project from HonestlyWTF. They have DIY instructions for this project as well.
Step 2: Materials
Door Knob - I got a cute flower one from Anthropologie for $6
Dremel - or a tool to cut the end of the bolt connected to the door knob
Step 3: Drill Hole
Step 4: Cut Door Knob
Quick tip! Keep the nut on the bolt when your cutting, that way you can easily take the nut off and it will still fit the bolt. If you don't do this and try to put the nut back on after cutting the bolt it wont fit.
[This picture is a recreation of something I did a couple weeks ago, that is why the bolt is short]