A good read at the best of times, "The Tough Questions Blog" has an interesting list of the top 143 business blogs/sites. The article is just a linked list, but it speaks for itself.

"143 Of The Best Business Links On The Web" starts out with some really top marketing sites, "The Engaging Brand", "commonsenseguy.com", and "Web Worker Daily".

There are more sites with loads of good reading that the list is nearly too long for me. However, just using the name of each blog in the list I tended to look at the blogs that had some sort of marketing idea in their name.

I recommend that you work through this list of quality business blogs yourself.