Some useful links:

The Homepage of Sage: www.sagemath.org

A site containing links for various computer tools for low-dimensional topology: CompuTop

The Knot Atlas: knotatlas.org

The Table of Knot invariants: KnotInfo

The GecoGedi Project Homepage: GecoGedi

An online version of Counter Examples in Tology: pi-Base

E-Mail Addresses:
collari[at]math[dot]unifi[dot]it
collari[at]mail[dot]dm[dot]unipi[dot]it