I've been struggling with Google maps till I found that someone implemented a wrapper so that you can use Google Map as an ASP.Net user control which is a great effort indeed. You can download it from this link.
However, after using it for a while, I've found out that it is storing the Google map object only once in the session and getting it from there whenever needed which was a problem for me that when you update the map in some page, you'll find it updated on another page.
So, I've digged deep in the code and updated it so that it stores the map object with a unique identifier that you set it as a property in the user control object like that:
this.googleMapCtrl.ControlID = Guid.NewGuid().ToString();
You can download the updated control files from here.
(Sorry the link is expired, if you want it write your email in a comment and I'll send it to you)