Pysochrone is a project mainly written in PYTHON and JAVASCRIPT, it's free.
Isochrone (contour) creation
pysochrone is a simple Python script for creating isochrone maps. Isochrones are curves of equal travel time from a certain point of origin. Really this can be used for any type of isoline (aka contour) map. For more information:
Code is heavily borrowed from the Quantum GIS Contour plugin.
The contour module has a class Contours which creates contour lines or filled contour polygons from an OGR compatible datasource. A cgi script, isochrone.py, uses this class to provide a RESTful service