An Abacus. For those that want to go old school on their math calculations. Or for when the end of the world comes upon us.

Print 4 towers
Print 2 bases

Glue towers together (2 sets of 2, holes on end are for filament to use to attach together)
Glue towers to base (Squares are for towers to be glued into)

Print 100 beads

Use plastic filament as rods between towers.

SUGGESTION FOR BEADS: Use Multiply function in skeinforge. For less strings, use the Tower function also.