It is small, easy to make, and uses very little materials.
-Very little materials
-easy to make
-Fun to play with
-Tends to spin in circles
-You have to get the balance right
-uses a special type of toothbrush
***UPDATES!*** (as of July 20, 2009)
I found the perfect toothbrush head!
Use the Exact Cross-Bristle Toothbrush I found at Superstore and it will go straight!
I give most of my credit to http://www.evilmadscientist.com because I discovered his bristlebot after I published this Instructable.
Step 1: Materials
-1x vibrating pager motor
-1x toothbrush head (bristles have to be angled as shown in picture 2)
-1x cell battery (any type, has to be between 1-9 volts)
-a piece of foam tape (already attached to top of toothbrush head)