The Pop-up book business is a very small world, indeed. It is, however, filled with many fascinating characters and nice people. Some of my favorite engineers don't seem to have web-sites [David Pelham, Kees Moerbeek, Chuck Murphy]. Others happen to be dead [Vic Duppa-Whyte, John Strajen, Lothar Meggandorfer, Voitech Kubasta]. Regardless, There is a lack of good web sites about "movable books." Most of the engineers mentioned here, I either know personally, or at least have met at some point. This list is in no particular order, and by no means complete.

There are other engineers I know, deserving much credit [Dennis Meyer, David Rosendale, Jose Seminario], now working in advertising, rather than publishing.

I discovered the "paper forest" blog not too long ago. There's really a lot of excellent stuff here.
http://paperforest.blogspot.com/

The Pop-Up Kingdom is an excellent site from Taiwan, with video. It includes books that are unavailable, here. Worth a visit, even if you can't read Chinese.
http://pop-upkingdom.blogspot.com/

This is a very good blog about pop-up books in Spanish.
http://librospopup.blogspot.com/

Marion Bataille took home the coveted Meggandorfer Award, presented by the Movable Book Society, for the best pop-up book of 2009-2010. ABC3D is a beautiful book. Congratulations to her.

Tor Lokvig has seen it all, worked on a million books, and is universally well regarded.
http://torlokvig.com/


David Carter has been in this business for quite a while, and has done a wide variety of imaginative work.
www.popupbooks.com

Steve Augarde is an engineer that I really admire. His books aren't complicated, but they often use difficult and unusual mecanisms.
http://www.steveaugarde.com/pop_up_books.html

Bruce Foster has also collaborated on an impressive range of books. Notably, his collaborations with Chuck Fischer. One of the busiest guys in this business.
http://paperpops.com/

I first started learning about paper engineering, while doing production work in Robert's studio. He is arguably the most influential paper engineer working today.
www.robertsabuda.com/

Matt is another guy I used to work for, and also a prolific author and excellent engineer.
www.matthewreinhart.com/

Kyle is an emerging artist/engineer from the same studio. He worked for pull-tab genius Andy Baron, as well and is currently teaching a very good paper-engineering class at Pratt Institute in Brooklyn.
www.kyleolmon.com/

Patricia ditto...
www.patriciafrybooks.com/

Another talented, new engineer. She also happens to work for me.
www.beccazerkin.com/

There are many good British engineers out there. I do not know much about most of them.
http://www.raymarshall.com
http://www.hawcockbooks.co.uk/
http://www.markhiner.co.uk/
http://www.pop-upworld.com/

A good place (besides ebay) to find rare books:
www.abebooks.com/

A nicely designed site dedicated to pop-up book criticism in French:
www.livresanimes.com/

Andre Pimenta is a paper engineer and teacher in Portugal
http://atelierdepapel.carbonmade.com/