Are there communities of practicing secular Buddhists? Religious groups are typically comprised of communities of practitioners who visit the temple/church a couple of times a week and practice together.  Is this true of secular Buddhism?  If so, Where are the largest communities?
Secular Buddhism is expressing itself in ways beyond the imagination. There are people in the virtual world Second Life that are practicing Buddhism virtually.
Secular Buddhist Association -- Supportive Virtual Buddhist Communities

There is talk of secular Buddhism all over the world.
(search for communities of secular Buddhists)

What seems significant is that secular Buddhism is taking off. I would say that people hunger for the Buddhist experience and practice without the masks of religion that various sects require its monks to wear. This is not the end to Buddhism but a glorious new beginning that is sustainable in modern culture.