http://www.kap.toadstone.com/wx/php/oswxmap_1.php
The mapping is zoom-able and I'll be adding a mouse pointer/lat/long display.
I know this is very parochial but I've been using the Open Space API for a while now and the mapping is very good. Ultimately the idea is to be able to call other Cumulus's users php file (if it exists) and display the data on the OS map. On a global scale the Open Layers API (on which the Open Space API is based) could be used. For Windows/asp users, Ajax could be used I believe.
Don't expect great advances quickly, I'm learning and have a heavy work load at work but it keeps me out of the pub when I'm away on site
Peter.