Yesterday, the New York Times reported that Yahoo is making a major mobile advertising play. Not wanting to play second fiddle to Google in the next great advertising market, they are striking preemptively, building the first broad mobile advertising network:

The company plans to announce on Tuesday that it is creating a mobile advertising network that will allow marketers to place ads not only on its mobile services, but also on those of other online publishers. And Yahoo is offering tools to help publishers customize their content for easier use with its mobile search service.
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The company hopes to start delivering text, display and video ads on third-party mobile Web sites by the summer, Mr. Boom said.
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Advertising on sites arrayed for mobile phones is a tiny market, but it is expected to grow quickly, and a number of companies, including the leading wireless carriers, are jockeying for position.

The Financial Times took a look at Twitter, a mobile mini-blogging service, that is "the talk of Silicon Valley."

Silicon Valley is abuzz over a new mini-blogging service for mobile phones that some predict will be a mass-market hit with the reach of a YouTube or MySpace.
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Users of Twitter post short messages – up to 140 characters – that can be viewed either on a website or on mobile phones. "Twitter probably wouldn't have existed before blogging, when people learned to be more transparent," Mr Mayfield added.
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Though launched publicly last summer, use of Twitter started to take off in the middle of March after it was adopted by technology bloggers attending the South by Southwest conference in Texas. As people like Mr Mayfield lauded the service on their blogs, interest spread quickly among the Valley's key opinion-formers.

Finally, we hear over at MediaPost that CBS is testing the mobile video waters:

CBS has struck a deal with Sprint to make ad-supported versions of "Jericho," "Evening News with Katie Couric" and other TV programs available on mobile phones.
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For the Sprint deal, CBS will include pre-roll ads as well as video ads during the natural breaks of "Evening News." Clips from other shows, including "CSI," and "Survivor," also will be available on Sprint as part of the deal.