Well, just thought this would be cool. There are probably tons of things people don't know about the Wii, like options and such. So if you found something cool that's not posted already, post it! (Try not to post something excessively obvious)
1. want to switch player two wiimote to two? or switch wiimotes? or just to turn them off? press Home -> Wiimote Settings (on the very bottom) -> Reconnect. This will turn off all Wiimotes and you can turn on the Wiimotes you want to use and choose which order you want them in without having to turn off the Wii.
2. Send your Mii to a friend: Go to your Mii Channel and click on the Wiimote icon on the right side. Drag a Mii to the circle above and choose who to send it to.
3. Email between an email address and your Wii: On your Wii, put the email address into your address book. Go online and reply to the message or tell your friend to. Now you can exchange emails.
4. When your Wii is glowing blue, it means that you recieved a message or Wii or is currently updating.
5. The path between your Wiimote and sensor bar must be visibly clear for the pointer to work. Since it's infrared, you can use a mirror to reflect the signal.
6. You can reset the game by pressing home and reset. This will reset the game and start over. Not reset as in delete all memory but restart it like as if you just put in the disc and loaded it up.
7. The rumble and sound volume can be adjusted via your Wiimote settings. Press Home -> Wiimote settings (on bottom)
8. If you are playing a gamecube game, when you eject the disc midgame, the screen will say to close the cover of the gamecube. If you dont' get it: There's no cover because you are using a Wii, not a GC
9. If you have any device that can use a USB to charge it, you can use the Wiis USB port to charge your device. I now charge my Zen Micro with my Wii sometimes
Add more guys!