vBulletin is now pushing their mobile suite, which lets you develop your own iPhone and Android apps. [vbulletin.com...]
Mobile access for community members is getting very important. IMO, the traditional browser, even with a mobile-friendly skin, is losing out to dedicated apps. I introduced mobile apps on a busy forum a few months ago and was really surprised at the volume of usage.
If you try the vB mobile app, be sure to post here and tell us how it worked!