Online, interactive, maps can be provided on web pages via JavaScript and a 3rd party Map Server. As usual, Google, is pre-eminent but Google reserves the right to include advertising with the maps it serves up.  For examples see the Handy Map at dalriada.org.uk  [actually now upgraded to use OpenStreetMap]. 
 
Notwithstanding the advertising issue, in Britain much better digital map products are available from our national cartographer, Ordnance Survey. For commercial use Ordnance Survey map data is quite expensive but recently it has been made much more widely available for non-profit use via OS OpenSpace, an Application Programming Interface (API) for dynamic mapping applications. 
 
However use of the OpenSpace map server is limited to 40,000 map tiles per website per day, which is not normally a problem.  See the RouteViewer site for an example, and zoom in and out to see the base mapping at various scales.
 
Also, there is a competely open source option – OpenStreetMap: