Alas, work in this space appears to be abandoned, too bad too because much could be done to improve robustness when writing with umounted aspects, or preserving security against attackers that can take images of the disk at different times.
Not to mention: integrating the results in standard software so the mere presence of the software on your host doesn't harm the deniability.
And http://dmsteg.sourceforge.net/
Alas, work in this space appears to be abandoned, too bad too because much could be done to improve robustness when writing with umounted aspects, or preserving security against attackers that can take images of the disk at different times.
Not to mention: integrating the results in standard software so the mere presence of the software on your host doesn't harm the deniability.