The TKIP solution is actually part of a framework called Wi-Fi Protected Access or WPA. It is an interim fix for WEP which is easily compromised. The WPA solution uses existing technologies like 802.1x and TKIP. It is meant for existing access points currently running the insecure WEP and have upgradable firmware which can then be used for WPA. With WPA, you can place your APs on the internal LAN.
The VPN solution is a very good alternative where you place your APs on the outside of the LAN. Users then have to connect via some kind of VPN client to reach the internal LAN.
The easiest and most secure solution will be 802.11i but this requires specific hardware that most current APs on the market lack. It uses AES-CCMP instead of TKIP. This IEEE standard has not been ratified yet as far as I know.
Since you are asking in a Cisco forum - currently, the Cisco APs that support WPA are the ones running IOS like the 350, 1100 and 1200. Otherwise, you can use VPN.
Check wi-fi.com and google for above terms and you will find lots of resources including on Cisco's documentation site.
I have not personally tried the VPN solution but WPA works great for me on a 350.
