Yahoo has released their competitor to the Google Maps API. I'm not familiar with the latter, but the main difference appears to be that Yahoo's maps can't be embedded in your own pages: the closest you can get is with the much-reviled frames. However, the popup windows shown on the map have links so you can direct people to one or more web pages at your site. You can see sample maps here.

[NOTE: This page refers to the legacy Yahoo Maps API.