Rose Pruyne, @rpruyne, posted a great presentation she gave from the Penn State Web Conference 2010 entitled "Usability and the Mobile Web." It includes some great numbers on usage and insights from Jakob Nielsen's "Usability of Mobile Websites" report (some more highlights from it). The "insights" get a little scary half-way through but the whole presentation closes nicely. Hopefully next year the crew at Penn State can open the conference up to outsiders. From following the hashtag, #psuweb10, it sounds like a great group of people and talks. Lots of info.