Classroom 2.0 just hit 9,000 members today. While I know that as a percentage of the population of educators that's a drop in the bucket, Classroom 2.0 is a social network that just addresses the use of Web 2.0 in education--growing, but still narrow, slice of the pie. And to have 9,000 people signed up there is way more than I ever thought there would be.
Ning in Education, another educational social network I run, just reached 1,800 members. It's a niche network as well that's growing quickly and exceeding my expectations. And the NECC 2008 Ning network has seen a flurry of activity in the last few days, almost 1,300 strong today, and really showing the value of a social network for an educational conference.
I will admit to a small amount of personal gratification in watching this happen and having been a part of it.