Boris Veldhuijzen-Van Zanten wrote a great blogpost in which he requested his readers to come up with the best SEO-tips. He collected all remarks and created a list with them, which he then converted into a nice WordPress plugin. For all readers who do...
There are a lot of sites describing how you could improve your Google Pagerank. They usually don't add any real new information besides "Make sure you are being linked to", "Use proper META-tags", "Make sure all interesting keywords are used in your TITLE...