There is also the ##polyphasers channel on freenode. While we've drifted a bit from only polyphasic talk, lots of regulars there did attempt to sleep polyphasically, some even a few times, so questions can be thoroughly answered. Also, since the people there are from all time zones, it is easy to find someone to talk to to keep you awake. Though that can apply to any moderately sized IRC channel...

Took survey, not yet contributed to the site, had lurked a lot over the past few months.