For my tunneling purposes, crypto is a must, though it doesn't have to be very strong. I was previously using ppp over ssh (And I still do, for non-linux machines), but for linuxlinux tunneling, this thing really rocks! And btw, the newest ver (check homepage) compiles as a module :)
Vtun as an alternative !
If you don't like to patch and recompile your kernel,
consider vtun as an alternative. Just compile and load
the universal TUN/TAP driver and off you go... (udp/tcp)
An open, cross-platform journaling program.
A scientific plotting package.