There are lots of examples on the internet and I have thought of making one myself a few times. It seems you trade the inconvenience of a long tube/large mount for the added complexity/slight loss of light transmission. Depends on your priorities. I guess the introduction of lower cost ED refractors has reduced the appeal of folded refractors somewhat.
Here is a link to a nice big one;
http://www.iceinspace.com.au/41-465-0-0-1-0.html
There is some good information here;
http://davetrott.com/telescope-proje...ded-refractor/