I've been hearing about the Medieval Institute Congress every May at Western Michigan University in Kalamazoo every since I've been in the SCA. And strangely enough, I have never gone. Not sure why, just never got around to it, even though I would likely enjoy it as much or more than the average SCA event. I am told they have an excellent vendor's hall.
Next year I have decided to attend, and probably to make a weekend of it, get a hotel room, etc. The conference lasts from Thursday to Sunday on May 8-11 next year.