It will already be able to work with any old USB keyboard, but if you want to go wireless, check this out:
http://www.411mania.com/games/news/80817/%5BWii%5D-Logitech-to-Release-Wireless-Wii-Keyboard.htm
http://www.411mania.com/games/news/80817/%5BWii%5D-Logitech-to-Release-Wireless-Wii-Keyboard.htm