Click here to read a great article by Tim Greenfield.
Click here to read an article explaining the configuration of a Fedora 8 Server using LAMP, Email, DNS, FTP, ISPConfig.
If you use other distributions take a look here:
Just use a published PAC (Proxy Auto Configuration) script and WPAD (Web Proxy Auto Discovery) protocol.
Click here to read the instructions by Jonathan de Boyne Bollard.
An article about this subject can be found in the Scott Lowe’s weblog.
Here are some useful guides to help configure VPN software clients using TheGreenBow IPSec VPN Client.
I’ve found this document on the Zyxel site for configuring Zywall VPNs.