The Internet Writing Workshop ( http://www.internetwritingworkshop.org/ ) has monitored critique groups for fiction, nonfiction, novels, romance, short prose, poetry, scriptwriting, and practice writing.
Each has small participation requirements, but the assistance and comradery are invaluable to writers at every level of development or success. IWW also has groups discussing the art and craft of writing in general, creative nonfiction, speculative fiction, and marketing. IWW membership is free.
To read about members' successes and learn about markets, check out IWW's blogspot: http://internetwritingworkshop.blogspot.com/ .