It is now possible to build TrueCrypt and use it with a standard OS2008 kernel. It requires the loading of the kernel module dm-mod.ko - which I've included in the deb. So if anyone would like to try it out, on the understaning that there's no promise it will work, or even that it won't break stuff, then the files needed are here http://mike.saunby.googlepages.com/truecryptforn800

I should probably add that my motivation was somewhat different, sharing encrypted FAT volumes between Windows and N810. So I've tested for quite different things. I say a bit more on my blog at http://mike.saunby.net and will post updates when I get more time to look at this. Could be days, could be months....