MagicMeets (www.magicmeets.com) takes place on July 14, 2007 in Harrisburg, PA, which by the way, is sold out.
MouseFest (www.mousefest.org) takes place at WDW for a week in the early December. It includes a 4-night Disney Cruise, along with another 4 days of informal meets at the WDW Resort.
They aren't related, except you'll meet some of the same Disney lovers!
We plan on going to both, in case you have any more questions.