Service Area Analysis

That's what we call this in Esri world - travel time or travel distance analysis may make more sense to normal folks. Here you are traveling on a road network - how far can you get over some time period? Two great examples via Google Maps Mania:

• Isocope - lot's of options for travel day, time, and mode (car vs. pedestrian). The link drops you into London by default, but Isocope works globally.
• HERE.com's Isoline Routing Example - very similar, but starts you in Berlin.