There are lots of great resources available on the Internet for learning more about programming and improving your skills. Blogs are one of the best, IMO. There's a wealth of knowledge and experience, much of it covering topics not often found in traditional books, and the increased community aspect helps to bring in multiple viewpoints and ideas.
We're probably all familiar with Coding Horror and Joel on Software (so no need to mention them), but what are the other great ones out there? What are the Blogs that you find yourself following most closely? Where you see the best new ideas, the most interesting or informative ideas, or just the posts that make you sit back and think?
One Blog per answer, and then we'll vote up the best so we can all learn from them.