I believe the last one was in April I think. And that wasn't much, just the Internet Channel support. I'm expecting a new one soon. Here's the history:
November 29: Blocked Wii Shop channel hacks by blocking DNS redirection.
December 19: Provided support for the Forecast Channel.
January 29: Provided support for the News Channel
February 14: Provided support for the Everybody Votes Channel.
April 11: Provided support for the Internet Channel: Final Version and added customizable Parental Controls for the browser
EDIT: From Wikipedia.