Microsoft's guide to their L2TP/IPSec VPN Client (Word doc file)
This June 2000 Microsoft Word document shows them deprecating their original PPTP VPN solution in favor of the new L2TP/IPSec VPN solution.

 This is the defensive "Microsoft's Head in the Sand" VPN FAQ page where they endlessly attempt to justify their brain-dead stance of deliberately not allowing their VPN clients to interoperate with other third-party equipment such as super-popular VPN endpoint routers. As a result VPN router users are forced to purchase ($39) and add third-party VPN client software to a Windows system which, essentially, already has it.

 A good Microsoft launching point page for many other MIcrosoft pages discussing and explaing VPN configuration and opertion.

 Microsoft's Step-by-Step Guide to IPSec
For users with fixed endpoint IPs this guide can be used for establishing very secure VPN tunnels between Microsoft systems.

Non-Microsoft Resources:

 Toms Networking "Small Net Builder" VPN FAQ

 Public VPN Service
PublicVPN.com is an inexpensive ($5.95/mo or $59.95/year) provider of PPTP and L2TP/IPSec services. Since it is compatible with with the existing VPN clients available for Windows, Macintosh and probably other operating systems, it represents a very useful means for allowing traveling road warrior users to obtain easy-to-use and affordable encrypted access to the Internet. As we know, this is especially important in WiFi and Hotel LAN settings.

The service's weaknesses are that since it uses standard VPN protocols, they are subject to being filtered and blocked by the user's local connectivity provider (WiFi hotspot, hotel, or ISP). Also, since PPTP uses weak authentication and PublicVPN's L2TP/IPSec uses a system-wide common pre-shared key known to everyone, there is little protection from determined man-in-the-middle (MITM) attacks.

Still, as a "much better than nothing" affordable solution, PublicVPN is definitely worth a look.

 HotSpot VPN Service
HotSpotVPN.com is a VERY interesting looking SSL-based Public VPN service. I'm in the process of learning more about it so that I can provide a full report.