Here is a list of resources to keep you up to date with mobile marketing

A great place to see whats happening in the mobile marketing world is the mobile marketing magazine.

http://mobilemarketingmagazine.com/

Their sister magazine Mobile retailing is also good for ideas and resources.

http://mobileretailmagazine.com/

QR Codes reviews and strategies

http://www.2dbarcodestrategy.com/

10 Ways to use CSS tables in your Mobile design

http://www.smashingmagazine.com/2008/08/13/top-10-css-table-designs/

Another Mobile Marketing Magazine

http://mobilemarketingmagazine.net/

Mobile Marketer magazine blog

http://www.mobilemarketer.com/

Linkedin mobile marketing and advertising

http://www.linkedin.com/groups/Mobile-Marketing-Advertising-62503?trk=myg_ugrp_ovr

A great place to find out whats happening in the mobile arena

http://www.mobilemarketingwatch.com/

A great video from a Google conference on the future of mobile marketing.

Found some great resources list them below in the comments.