After using a co-worker's quick adjust F-style clamps, I knew I had to have a pair. The only problem, however, was that the good ones were very expensive ($70 plus per clamp) and the affordable ones didn't seem very strong. So, left to my own devices, I used some leftover metal stock that I had and made them myself.
They work very well and they are very strong. The most challenging part of making these was coming up with a good but simple swivel design.
Total cost that I have in both clamps is about $15 for the 3/4" threaded rod and coupling nuts.
Here they are: