Natally is a NAT/VPN program that works on a Linux host that cannot do tun/tap (Like many VPS's). It requires basic iptables functionality and be able to create raw and packet sockets. Natally blowfish encrypts its traffic to the client.
Natally was written because I wanted a VPN on my Virtuozzo VPS.
You can download natally as a tarball here.
or you can download natally through subversion with the following command:
svn co https://natally.svn.sourceforge.net/svnroot/natally natally
You can also use a web interface to browse the sourcecode and changes.