Bob Sutton has a new blog entry that reproduces a list of the most popular management blog posts at Harvard Business Review. Bob is happy that his post is rated number one. I liked his, as well as a few others. If you manage anyone, then you'll likely find some good advice in there.
Another recent HBR blog post I liked wasn't in the list. It's titled "Are You a Good Boss - Or a Great One?" I think its message is also applicable if you replace "manager" with many other domains, such as "engineer" or "student" or "athlete" or (you get the idea). I think it's common for all of us to stop working on our skills, and even to observe that as long as we're not failing then we must be doing ok.