Yahoo! teamed up with Research In Motion to bring several of Yahoo's mobile products to the millions of BlackBerry users. Those products specifically include Yahoo! Go for Mobile, Yahoo! Search, Yahoo! Mail and Yahoo! Messenger. BlackBerry owners can activate the new features for free from Yahoo's site.
Yahoo, like Google, has been making an increasing number of plays in the mobile space lately. It's not just software--earlier this year Google teamed up with Motorola to have phones ship with a dedicated "Google key", though none of those models have shipped yet.