Exped is the originator of the two-person sleeping mat and we have one in every category - car camping to ultralight backpacking.
Before our duo sleeping mats came along, the only way to sleep side-by-side with a partner in the backcountry was to attach two single mats together. Technically this works, but the gap in the middle, where the two mats meet, is not at all ideal. We don't have a slot down the middle of our bed at home, right? The duo mats fix this issue and make sleeping with a partner much more comfortable. Used with an Exped Mat Sheet or Cozy Sheet and DeepSleep comforter is amazingly comfortable.
For backpacking, paddling, bike touring there a couple mats to consider: SynMat HL Duo (below), SynMat HL Duo Winter (20 denier fabric) and SynMat Duo (50/75 denier fabric) These tapered mats are light, compact when stowed and come in medium and long/wide versions. They are insulated with synthetic, lofted Texpedloft and vary in warmth depending on application. These mats also have two chambers, one for each sleeper, for individual firmness.
At the other end of the spectrum are the SIM Duo mats. SIM stands for self inflating mat: these are foam insulated, which aids in the inflation process by expanding and drawing air into the interior when the inflate valve is opened. Representing this group are the SIM Comfort Duo 5, SIM Comfort Duo 7.5 and MegaMat Duo 10. They are thick and plush, with a skin-friendly stretch tricot top surface and fit well in truck beds and SUVs with the rear seats dropped flat. They also double as excellent guest beds!
With a Mat Sheet, DeepSleep comforter (below) and a couple Exped air pillows any of these mats will rival your bed at home.
There is also a mat built for travel. The AirCellMat Duo 5 (below) is built with multiple cells to smooth the rough surfaces often passing for beds in hostels and hotels around the world. This mat is also excellent when used in a hammock, comforming well to the shape of a hammock sleeper.
So there's a duo mat for nearly every user (certainly some we haven't heard of yet!).