Not sure if you guys can source them in the States, but we usually use either poly-vinyl covered foam mats (with a density of about 45 kg/m3) or tatami style mats (straw-filled, vinyl covered). These mats are positioned within a very simple pine wooden frame, simply to stop the mats moving. We've installed them on everything from sprung wooden floors through to hardened cement floors.
The mats are relatively hard (they certainly ensure that you are a little more careful with your ukemi) but are very easy to place, extremely durable, and are very transportable.
(page 3 - mat #14)
The link probably won't help much as its an Australian site, but it might at least help point you in the right direction.