Here's a list of some cool DIY fitness equipment (note - I haven't tested most of these. Will annotate with results and lessons learned after I've made them):
2-Wheeled Ab Roller - this is awesome because these things are super-sturdy, last forever, and you can do one-arm roll-outs (which are super badass).
Homemade Dumbbells - dumbbells are pretty expensive, so it would be nice to be able to make your own loadable dumbbell. Here are a couple different ideas:
From this forum, using 1.5" galvanized pipe and couplings
Even simpler, just 2" pipe and hockey tape; however, note that 2" pipe has a 2.375" outer diameter, so a lot of plates won't fit. Just use 1.5" pipe (it has a 1.9" outer diameter) if you're worried about this.
Farmer's Carry Handles - found a couple interesting methods for super easy construction (and cheap).
This method uses a 4x4, floor flanges, and some pipe.
With rope and a piece of pipe, you can create an extremely cheap farmer carry implement. Found here.
