Racherbaumer's "Marlo on Erdnase" contains a nice section (about 20 pages) on the riffle shuffle, culled from Marlo's work. It's one of the books Houdini Magic included in the pre-order package with the Ackerman Erdnase DVDs, but it's also listed on Houdini Magic's web site as being available for purchase separately.
Don

Fulves' material is somewhat hard to come by, but worth it when you finally track it down. Keep an eye on the "for sale" sections on here and Genii, and search on ebay for "Fulves" every couple of days. It might take some time but they're definitely findable. They also tend to go for lower prices than the Marlo manuscripts, although I did see RST part 3 go for over $200 on ebay recently, which I believe is a bit much... I got the other ones for around $40-$60 each over the last year or so.

There's also some interesting riffle shuffle work in the Crimp #15 (Major D'alby's Brag Stack) and variations on it in by R. Paul Wilson in Magic Magazine (can't recall which # exactly, it was the Karrell Fox memorial issue).

I know that Fulves Riffle books are hard to get. I have almost all his books on Riffle. Only one is missing and it is Riffle Shuffle Methods.
I would like to by copy but do not know where to search for it.

There is a relative unknown little book called 'New Card Control Systems' by Joseph K. Schmidt. I think it was edited by Kaufman. Book dedicated to hands stacking with riffle shuffle.

Beside Darwin Ortiz there are 2 gentlemen that have some nice shuffling work in print Jack Carpenter and Ernest Earick (By Forces Unseen)
I don't remember the book by Carpenter

Jack Carpenter's book is Modus Operandi, one of my favorites.

It is right, it was published by Kaufman/Greenberg 1995,103 pages, 1000 copies.