I think the best (and first) thing that comes to mind when I hear the words "DIY Photography" is Tinker Tubes for the late Dean Collins.
With just a few dollars worth of PVC piping Dean shows us how to make light stands, reflectors, scrims, even a diffuser that will fit over your garage door.
You can get the 27 page PDF of Tinker Tubes designs, material list, detailed demonstration images, and everything else you need to know to make some pretty cool gear here for free, but the scan quality is rather poor (to be kind).
Software Cinema is offering the high res version as an instant download for just $19 and they are throwing in a Dean Collins studio sketchbook for free.
If you want to see what other folks have done with Tinker Tubes check out Thomas Evans post here and the "Ghetto Studio" from Just Fab.