Well, may as well start us off with a GBAtemp list of Wii friend codes.
In case you dont know where to find yours, go to the message boards > then bottom right second button > then address book.
Also post your e-mail, as you can send e-mails+pictures from WiiPC.
Go to your address book and register a user with the email. In about 5-10mins, that email will get a letter saying that person has added you. Simply reply and send, then your registered! Freely send letters with your Wii and PC.
Your Wii e-mail address is: w{your friend code here}@wii.com
Also we can transfer Mii's and stuff through the Parade option or something. Haven't tried it.
My code:
4389 1791 6207 8819
The Wii fucking rules BTW!