If your friend code list is currently a bit lacking you might be interested in the relaunch of a website with the sole goal of creating a community of DS (and Wii) gamers and enabling them to exchange friend codes for online play.
OneClick Wi-Fi launched just a few days ago, and once registered it enables you to enter your friend codes for all of your wi-fi supported games. You can then use the site's matchmaking feature to meet other players with the same games.
