It occurred to me that Steven M. Bellovin wrote in gmane.os.netbsd.general:
> On Sat, 27 May 2006 08:22:14 +0400, "Rakhesh Sasidharan"
><rakheshster@gmail.com> wrote:
>> Hope that helps. Maybe you can go with FAT32 (all OSes seem to have
>> support for FAT32 anyways) instead of ext2fs or anything else.
>> 
> That's the best choice, I think -- I don't have to worry about installing
> Windows drivers on other folks' machines.

I don't know if it's going to be an issue for you, but there's one subtle problem
with FAT32: It has a 4GB file size limit, which isn't that much anymore these days.