This is not a question- it is an answer. I just got off the phone with Chris at Technical Support and he was excellent, but this should be in the forums as well.
If you use an Apple Airport product (Extreme or Express), and you want to connect your Wii to the internet wirelessly, there is a crucial step that is not listed on the websites.
If your Wii does not see your wireless network, it is likely a problem with your router. I use a Mac, so I cannot speak to how to accomplish this with PCs (perhaps someone with a PC and an apple airport product could respond?) but on your Mac, open the Airport Utility.
Select your wireless network and then select the tap at the top of that window marked "Wireless"
Down the list of details you should see one field marked "Channel". If this is set to "Automatic", your Wii will not be able to lock on to the signal from your wireless router. Make sure to set the Channel to "1", and then Update your settings.
Once the wireless router has had time to reboot, try searching for available wireless networks on your Wii again, and it should show up. Plug in your password and you're ready to rock.