I am a fan of the Sven also, but it doesn't meet your requirements for a blade that folds into the handle. I have a few of those folders, no idea what brands. What I can tell you is to get a quality brand name. Don't get one of the generic types found on the "camping" wall at the local discount store. Those usually have badly designed teeth, and are made of a soft, thin, material, which tends to bind in the wood, then the whole blade buckles and bends...

A couple of years ago my smarter half got a "What-A-Saw" for me It is a little heaveier that some others but has 3 blades in it. I have used it a number of time to cut everything from green wood to steel and it has worked well.

The one in my Swiss Army Knife is small but good

I've used a fast bucksaw for 20 years and they are very nice.

http://www.fastbucksaw.com/

They cut well, are well made and pack down small.

That looks like it would be fairly easy to make.

I do have a friend who in fact made his own.

Kershaw also manufactures folding saw.
http://www.kershawknives.com/productdetails.php?id=169&brand=kershaw

fooman: This saw from gerber looks good too.

I use a folding/pruning saw currently when camping. While the aggressive teeth cut very well I find that the hand positioning is awkward for longer sessions of wood cutting (fortunately the kids are getting old enough to learn to deal with sharps... can you remember when getting to cut firewood was fun and exciting?).

I am thinking of swapping to a portable buck saw like this:
Portable Buck Saws

That will change my hand position to a more traditional, straight armed grip.

Wengergrip all the way.

I'm not sure how available the brand felco is in the us, but I'm very satisfied with the following saw.


felco saw