There is a community group on RDF Stream Processing http://www.w3.org/community/rsp/
and it's mailing list: http://lists.w3.org/Archives/Public/public-rsp/ (empty ATM) that has just kicked off in W3C.NB Community Groups are easy to start (it just needs 5 people to says "it's a good idea") and have no deliverables or timeline. They self-organise.
Andy
