For the past 9 months I've being telling everybody I know that I am going to build a bed for our guest room. Well, at last I got around to actually building it, to my wife's delight! I base this bed on an Instructable I found by William Holman. (Box Bed)
I simplified the build a bit because I don't nearly have all the tools William have. I must also submit that I could simply not afford plywood and settled on 18mm MDF instead.
This build came about when we emigrated and needless to say, money is an issue and we get family visits from time to time and it is not cool to let your wife's parents sleep on a matress on the floor.
All the materials used are readily available at your local hardware store. I also had the MDF cut at the hardware store to simplify the build (and I also do not have the tools or space to cut it).
UPDATE: Unfortunately, my better half decided that she want to upgrade our bedroom suite and we decided that our current furniture will move to the spare room. Needless to say, no more bed to build. I will still put some Sketchup files and jpg's up here if anyone would be interested in building this box bed.