Moz.com is a great resource for any knowledge level. They offer advice spanning from strategic level through to in-depth technical tutorials.
A lot of the online marketing sites as I'm sure you see are geared towards online entrepreneurs. 2 great sites I believe Brick & Mortar business owners can receive great online marketing take-aways are Social Media Examiner & Duct Tape Marketing. Both always have great tips that SMB's can implement in their business.
I consult for a brick & motor family run retail business that has about 50+ stores throughout the country. How can I help?