http://www.leapfrog.com/en/leapfrog_parents/preschool/language_and_literacy/printable__letter0.html
They have some others too, looks like you have to have a (free) account to view some of them below. I haven’t dug through all of them yet, but looks like good stuff.
http://community.leapfrog.com/t5/Other-LeapFrog-Toys/Letter-Factory/td-p/1049