Promo Sheet/Flyer--your promo sheet should be loaded with great quotes from reviews about your book. If you don't yet have professional reviews, use testimonials. Put an image of your book on the sheet. Use it to hand out to prospective readers. Stand near your sales area and direct those readers to your sales table for actual purchase.
Bookmarks--nice bookmarks with brief information about your book. Bookmarks take the place of business cards and should have your URL and general contact information along with where to purchase the book.
Large poster board of book cover image--an enlarged poster-size image of your book cover created on a cardboard of foam-core backing to protect it. Do not date anything on the image so it can be easily reused from event to event. Bring a sturdy stand to put it on.