There was some discussion on here a while ago about someone on e-bay selling fibers in something like 50 foot bundles. Here is a site that you can order it by the foot or meter if you want with out having miles of fibers laying around the house.

The flourescent (colored) fibers sell for $1.80 per meter for .020" and $2.25 per meter for the .030" fibers. They come in red, green, yellow, orange, and violet.

I just ordered some white (unjacketed fiber section) for 9 cents per foot and some of the violet above.

http://www.fiberopticproducts.com/