MapWii.com is a Wii-inspired application of Google Maps that makes locating and making potential Wii friends manageable. Even better, MapWii has been designed for Wii's Opera browser. To join, you'll have to give up your friend code, nickname, city, country, and zip (all additional information is optional).
The database is limited in its current state, both in number of registrants and scope. You may find yourself with a Wii full of friends, but it's impossible to know which ones will stick without much trial and error. In this case, real-world location isn't as important as play-style or genre preference. A few more fields of required data and MapWii could go a long way toward hastening the 'matchmaking' process.
See also: Web sites step up to connect Wii owners