The website of the late W4RNL is a good place to start reading:http://www.cebik.com/content/radio.html
Yes, you have to register for free, but it goes into a lot of detail on many
antenna designs, including some portable yagis, loops, etc. His Moxon
design has become a standard for light-weight beams with good performance.
DK7ZB also has some designs for portable yagis: http://www.mydarc.de/dk7zb/start1.htm
The HexBeam can be built to fold up like an umbrella:http://www.karinya.net/g3txq/hexbeam/
What works for portable operation depends on your constraints - certainly
it is different for backpacking vs. Field Day vs. a week in a vacation condo.
You really have to define your parameters and limitations - weight, size,
setup time, favorite bands, available supports, ground characteristics, and
whether you are interested in random contacts or DX, etc. - before choosing
the antenna that best fits your needs.
For myself that has usually meant wire antennas because they are easy to
transport and cheap to make, and I often have trees for supports. (Otherwise
I use the 4' military mast sections, which I can stack to 40' by myself.) But
other than Field Day much of my portable operation is on 40/80m, where simple
dipoles are quite adequate in most cases.
If you look around the web you should find instructions on how to modify a
tri-band yagi so the pieces fit in a golf club carrier for DXpeditions. Basically
the elements are cut and short pieces of thinner tubing added inside to make
additional joints where the elements can be disassembled. Rather than hose
clamps, aluminum pop rivets are used to assemble it, then drilled out when it
is time to leave. I haven't done this to my TA-33jr because I can manage the
boom and elements in my van, even if they have to stick out the window.