Ponk Room Maps
An example of Microsoft's Bing Map system
Well, here on the left is the Microsoft Map, which works very well. A well documented API, which, if you have used Microsoft software previously, is not difficult to navigate.
The API key is different for each domain, but it works OK on my localhost, so no need to upload the page to the domain registered with Microsoft in order to test the map.
It can show Ordnance Survey maps if the location is in the UK. This is an excellent option. Click top right on the button which says "Road" by default. I think the map colours are better than those on Google Maps too.
This version is free to use if you are not a business user, trying to make money from your site. At least, I think it is - this is not very clear from the MS blurb. But, this being MS, they would charge for the API key if it was not a free product, wouldn't they ?