iVPN

Until now, only users of Mac OS X Server could make use of the VPN servers that are based in the standards PPTP and L2TP and included in OS X, and which are dedicated to the creation of virtual private networks.

iVPN is an app with a graphical user interface that enables you to use both of those standards on a non-server Mac. Just don't use iVPN on a Mac OS X Server, because according to the program's author, you won't be able to go back to using Server Admin to configure the VPN server.

It's very easy to use: just enter the username and password that clients will use to connect to the server, and the range of IP addresses that will serve those clients.