There are a lot of places you can get the riser cards from ebay so it won't be hard to get good cheap risers.
Thanks for the info. I've always been interested by the idea of getting some risers to save a lot of money versus buying whole motherboards for the sake of extra PCI-E slots to squeeze more graphics cards on board. What's the story with the extended ribbon cables? Is the idea to just rig up the graphics cards just any old way they can fit inside whatever case you're using them with?