One of my favorite reads on the net is the Working Knowledge e-newsletter by Harvard Business School. Just out is their list of the most popular articles from 2007. This is necessary read for anyone who is in a leadership role and I recommend it highly. From their list, here were my favorites:
How Much of Leadership Is About Control, Delegation, or Theater?
The Key to Managing Stars? Think Team
Sharpening Your Skills: Negotiation
Podcast: The Authentic Leader
How Do You Value a "Free" Customer?
This is a very good resource. I encourage you to find your own favorites!