To demonstrate how it works, HopStop has put together mashups with Google Maps, MapQuest, and Yahoo Maps. For each of those, you can download code to get you started on implementing HopStop on your own site.
While HopStop faces some significant competition in providing mass transit directions from the likes of Google Transit, they have beaten them to the punch in offering up an API. And while HopSpot services fewer cities, it’s the huge metro areas that it does have indexed where its service is most useful and where they’ll likely find the most interest for its API.
HopStop is offering a free version of the API, which is limited to 1,000 calls per day. If you need more, there is a premium version that also lets you private label the feature - a good business model for HopStop if they’re able to attract high volume retailers within their target cities. HopStop also makes money on local advertising.
Despite the competition, HopStop is doing well – Compete shows the service almost doubling its traffic year-over-year, and the company claims to be reaching nearly 2 million visitors each month.
Additional Resources from Mashable