Todays news on this subject from the Aus-Soaring group...
In North America, you should be able to watch tomorrow's tracking
each evening.
It looks like you can overlay select BLIPMAPS too.
Jim

Our tracking has been very successful over the last month and we are
in the progress of expanding our system to better support club
operations and self management.
We are now on to our third competition - the Victorian State Champs:

http://track.glidingmaps.com/event/gcv/current/display

Some work has gone into improving IE support, but it is still very
flaky - so I recommend Safari, Firefox or Chrome.
Enjoy
Scott