Give your wii a memorable email address:
1) Open up a gmail account (for example: Gilswii@gmail.com)
2) Send an email from your wii to the gmail account
3) When you receive the email in gmail, reply to it to confirm the account
4) Make a note of the "from" address. This is your wii's unique email address
5) In gmail settings, enable POP forwarding
6) Set up a filter to forward all email sent to the email address (for example: Gilswii@gmail.com) to your wii's email address that you made a note of in step 4.
Et voilla! Just give people the gmail address, and every email they send you will appear on your Wii!