At Sleuthfest, the Keynote speaker is John Hart (Oline Cogdill had a great interview here) and the Guest of Honor is Brad Meltzer. You can check out the festival web site for the many other authors scheduled to appear. If you're on Tweeter, the BookBitch Blogger will be sending out tweets from the conference all weekend.
The South Carolina Book Festival covers many different disciplines, but has mystery writers, as well. The Guest of Honor is Scott Turow with other authors scheduled including JT Ellison, C.J. Lyons, Austin Camacho, Alexandra Sokoloff, Mignon Ballard, Kathryn Wall, T. Lynn Ocean, Fran Rizer, Vicki Lane, Charles Todd, Karen White, Ronald M. Gauther. Ellison (a/k/a Thriller Chick) is tweeting from the conference there.