If you are interested in marketplaces for online therapy, have a look at Ingenio[1], which has been in this space for a while. Ingenio was acquired in 2007 by AT&T [2], supposedly for its patent portfolio, but it continues to operate.

[1] http://www.ingenio.com/ [2] http://techcrunch.com/2007/11/19/att-acquires-ingenio-and-th...