Hey.

I managed a few weeks ago to connect my N9 via VPN9c to my FRITZ!Box.
And then thought heck this should work with my N900 the same way. And guess what? It works

Now both my darlings connect per VPN to my Home.
You need (from repo, I used devel):
vpnc and vpnc-gui
vpnc needs some patching (you have to exchange the executable /opt/maemo/usr/sbin/vpnc with the attached one)

Here are the threads:
vpn on n900
vpn9c
And some important links:
info
solution

All credit to harbaum (for vpnc), harbaum/scriptkiller (for vpnc-gui)
and imagomundi (for the FRITZ hints).
Thanks to too (for vpn9c)