An update for the Wii came out yesterday (Firmware 3.0). In addition to adding a digital clock to the channels menu, the update allows for USB keyboard support in the Shop Channel, Settings Menu, and Message Boards.
There is not yet any keyboard support for the web browser, but one imagines that it won't be too long until it is supported.
The update also made ineffective the Freeloader discs used by some to play imported GameCube games.
To get the update, click the "Wii" icon in the lower left of the channels menu. From there go to "Settings" and then scroll to the third page for "System Update".
Thanks to Dan D. for tipping us off to this last night.