Hi... DW and I just got a new Ford F-150 quad cab. There are storage units you can get that go under the rear seat, but they are close to (OR OVER!!) $200. Yikes.
I tumbled onto this fella on the F-150 forum site - and HIS DIY solution LOOKS better and IS BETTER than the $200 Plastic boxes. I did one and i figger $25-30 depending on what you can score for carpet. That beats the bejesus out of $200!!!!
Dunno about OTF (Other then Fords), but if your rear seat folds up, to explore!
Here is the link to his Project / pix / discussion.
Have fun and POST PIX / Suggestions.