This article is a travel topic
Running as part of a vacation has seen strong growth in recent years. Individuals wanting to complete marathons in different cities, states, or countries can do so with the numerous marathons offered in the United States and abroad. The Boston, New York and Chicago marathons are three of the largest in the country. Not suprisingly, Honolulu is a top marathon destination of choice as well, due to Hawaii's travel appeal. Companies such as Marathon Tours and Travel  operates tours that take traveling marathoners around the globe.
Marathons are not the only possibility for running on a vacation. Endurance races are also available, and running shorter distances are also available. Run the World  operates interesting culture/running tours to international destinations, and allows a traveler to run, but still soak in a large part of culture, which is often missed on a marathon trip.
The Hash House Harriers  are a running club that originated among expats in South East Asia but has since spread widely, with well over a thousand groups in many countries. They do a weekly hare-and-hounds run, followed by a gathering at a local eatery. There are frequent regional gatherings called "interhashes".
Here are some of the best places in the world for travelers to run; that is, routes that lend themselves to site seeing and a good jog.