Alternate Bases

TeachingCollegeMath.comOnline DemosArithmeticAlternate Bases 
Base 10 Blocks and Exploring Other Bases (2, 5, 8, and 16)  This interactive tool comes with lesson plans to help you incorporate it into your class.  I will probably use this one for my Math for Elementary Teachers class, which does a lot of work with alternate bases, in an attempt to understand the algorithms we use for base 10. (contributed by Maria Andersen, MCC, June 2007)

NLVM Chip Abacus: This is a website that deals with place values and has a chart on it where the teacher is able to add and take away from each place value. Not only does it do base ten, but it also does base 2 and 5. This is a good tool for the teacher and students. It is called a chip abacus. (contributed by Alyssa Nauta, MCC Student, Winter 2007)