Two Google maps posts in a row? Not surprising when you consider that I enjoy looking at and analyzing maps.
Anyhow, not sure if these have always been here (maybe I've just been missing it at all these years), but I found that the Metro and South Portland bus stops and schedules have been integrated into my Google maps. I think these have been an option for Google Earth but I never noticed the integration on regular web maps until recently. They seem to be accurately placed and also link to a current time table of upcoming buses.
This isn't quite as helpful as I imagine open transit data would be, which would allow developers to build applications which track the real time location of Portland's buses, but it's a good step in that direction.