I wanted a portable, lightweight and inexpensive platform bed substitute that I could put together and take apart at will and whose individual pieces I could carry in my car when I move. I did find a few metal bed frames that seemed at least somewhat portable - http://www.walmart.com/ip/Smart-Base-Bed-Frame-Queen-King/10924588 for $109 for example, but found them too heavy and unwieldy. I didn't think they would fit in my car when moving, and in addition, I thought the steel edges would tear up my planned improvised mattress out of several sleeping bags. After a lot of research, I found a solution that is working great for me. The items are easily available in a standard, international chain (IKEA) and each individual piece weighs just 10 lb and measures (as packaged) 22" W x 2.125" H x 33.125" L. You need no tools to assemble it and the improvised platform bed costs (as of 05/26/10) just about $96.
Note: I am also using an improvised mattress made out of eight $9 sleeping bags inserted into a zippered vinyl mattress cover to go with this DIY platform bed for a complete, inexpensive, portable, lightweight bedding solution. Details are at http://www.instructables.com/id/DIY-Mattress-Substitute-Portable-Inexpensive-L/