You can add Google Maps to your website or app using the Google Maps JavaScript API. There is a guide to getting started here: Google Maps Getting Started Guide
TileMill is a program that lets you import different types of map data and build your own maps. You can change colors and textures, add markers, and export for use in web and mobile apps. TileMill Website
MapBox MapBox is a site that let's you store all the maps you create with TileMill so other people can view them. MapBox Website