Actually, 2,870 at last count. Over at
Drawn!, Robot Johnny
reports that Flipbook.info has a huge collection of vintage flipbooks on display, including clips of them being animated—thumb, forefinger and all. The site's in French, but you shouldn't have much trouble navigating it.
By the way, if you're af flipbook fiend, you might be interested in Ruth Hayes's article on making your own flipbooks and zeotropes in the latest
fps. Also, stay tuned for more info on the
Cinémathèque québécoise's upcoming flipbook exhibition.