I saw a message posted by Megan Smolenyak Smolenyak on Facebook about how people are using Twitter to find DNA participants. She said she heard about it on the ISOGG mailing list. I googled "ISOGG" and found the International Society of Genetic Genealogy website. It is free to join, so I filled out the online form and submitted it. I also requested to join their yahoo group for DNA-newbies.
Update 7/15/09: I still have not received confirmation that I have been approved to join the yahoo group. I sent another request today and I hope they will approve me soon.
I assume that when she said "mailing list" she was referring to the yahoo group because I don't see any other mailing list on the ISOGG website. I am very interested to know how twitter is being used to recruit DNA participants!
I have been very active with our own Godwin/Goodwin/Goodin Surname project at Worldfamilies.net. You can read about my Godwin and Smith DNA activities here.