>
> I want to store my ssh keys, gpg keyring, and various other files
> on a USB flash device. I'd like to have it look just like FFS (with
> appropriate permissions, etc.) when mounted on a BSD box, but I'd
> also like to be able to access these files from a Windows box in an
> emergency.

emergency?? in emergency usually NetBSD is used to access windows 
partitions.

>
> Is there anything for MS-DOS systems along the lines of Rock Ridge for
> ISO 9660 filesystems that would let me use an MS-DOS filesystem under
> Unix as if it were a Unix filesystem with the usual metadata, links,
> etc., but actually store everything on an MS-DOS filesystem?
>
only long file names.

linux have option to store all needed unix data in one file per directory 
- they did this to make option of installing linux on MS-DOS partition.


> Failing that, I'm open to other suggestions. My only other idea at
> the moment is to divide the USB flash memory into two partitions and
> regularly copy the Unix stuff to the DOS partition.

or keep your data as .tar.gz files on DOS partition