Some sites of pianists that specifically label themselves collaborative include those of Hugh Sung, Rebecca Wilt, Amanda Johnston, Philip Voldman, Lisa Reynolds, and Karen Lee-Morlang.
A very interesting project of Hugh Sung is the recently started Collaborative Pianists group on Myspace.com. In addition to a members' roster that at last count had 244 members (with musicians of all backgrounds), a forum, and a bulletin board, Hugh states that one of his goals is "to create a worldwide network to connect instrumentalists and vocalists with pianists who understand the fine art of musical partnership and support", a goal entirely possible given the capabilities of the Myspace platform.
A similar type of network already exists on sites such as the list of Piano Accompanists in England, Ireland, Scotland, and Wales, although this is more of a service-oriented directory than a place to put together musical partners.
An entirely new type of organization is Collaborative Works in Chicago. Set up as a limited liability partnership consisting of Shannon McGinnis, Nicholas Hutchinson, and Jerad Moseby, Collaborative Works is a "vocal coaching studio and collaborative arts institute" where partnership and collaboration are built into their core values and advertising:
What sets Collaborative Works apart? Our collective experience and the wealth of repertoire we've studied and performed make us the ideal one-stop resource for your next project. We take pride in our work and bring professionalism and artistry to each and every project. We believe that good sight-reading ability, while a necessity in our fast-paced business, does not by itself create a good accompanist. Therefore we make a commitment to arrive at each and every coaching, rehearsal, and lesson, as close to performance-ready as possible. Strength at the keyboard can only make your work stronger, and security in our own playing allows us to focus on you.
With the recent growth (proliferation isn't the right word to use, yet) of collaborative piano sites in the last year, it will be interesting to see what new sites are created in the next while. Stay tuned...