http://oneclickwifi.net/
Ok I started up a VGChartz group. Everyone go sign up and put in your friend codes! :p They have an online buddy list type thing so you can see who's online and search by game and stuff too.
Here's a version optimized for use with the Wii's internet browser:
http://wii.oneclickwifi.net/
And a version for use with the DSL browser:
http://lite.oneclickwifi.net/