Isochrones

Both Mapzen and Mapbox offer Isochrone computation services:

• https://mapzen.com/blog/introducing-isochrone-service/
• https://www.mapbox.com/blog/announcing-isochrones/

Software for both is Open Source so you can run it yourself, or register for a free API key and use their servers within some limits.

You can use the TravelTime API to draw an isochrone on OpenStreetMap, it's free to test and works for driving, cycling, public transport and walking. Here's the documentation to get a key and make your first request http://docs.traveltimeplatform.com/overview/introduction

(Disclaimer I work for the creators of the TravelTime platform).

There is an isochrone wiki page that lists various examples and softwares.