I setup pingdom to track plan9.bell-labs.com -- it routinely checks from several "probe" server scattered across the world so its a good resource to check when you are trying to see if its your problem or if something is wrong at the Labs. I've got an email notification relay setup too, but haven't confirmed that its working.
The report is available here: http://www.pingdom.com/reports/ny7spbpcwjfu/ and the mailing list for the notification relay is here: http://groups.google.com/group/9nag (Yes, sources was down for 4 hours this morning) -eric
