sshuttle is just awesome:
Transparent proxy server that works as a poor man’s VPN. Forwards over ssh. Doesn’t require admin access. Works with Linux and MacOS, now including 10.6.
And it is easy: ./sshuttle -r username@sshserver 10.0.0.0/24
That gives you a VPN to the entire 10.0.0.0/24 subnet.