a science game: "a virtual Darwinian aquarium .. you initiate a primordial soup, and .. check up on what Virtual Mother Nature is up to - about every 15 min. (or every few days)"
basic concepts broken down into useful small steps, with many visual examples to guide process. Web 2.0 in that it provides for interaction and author's introduction to sections.
Firefox extension offers an addictive way to search via categories or keywords or happenstance; you train it, with thumbs up or down on sites, so it learns your tastes; I prefer searches on keywords so far, and have had little desire to "network"