I found this post about Google Maps about Click To Call
I don't know if you already know it

http://juberti.blogspot.com/2006/11/google-maps-adds-click-to-call.html

CED

That feature was actually showing up for me yesterday at about 11am but is now gone. Here was the help page linked next to the "call" link:

http://maps.google.com/support/bin/answer.py?answer=52512&topic=1467