If you like Wikipedia, take a look at a new site called VisualWikipedia. It contains the same information as Wikipedia (All article text is derived from Wikipedia and licensed under the terms of the GNU Free Documentation License- the site has no connection to the Wikipedia organization) but presents the information differently, more visually. It makes iteasier to navigate the huge amounts of information. When you point your to one of those many internal Wikipedia links a window pops up showing the first paragraphs of text on that page - so you can find out if the page is of interest before you click.
Other features: each article is followed by a tag cloud and often a mind map detailing how the subject of the article relates to other concepts; and in the right margin of the articles you can browse related YouTube videos. The Main Page has news articles, a featured article, a section of "On this day", and some interesting factoids from recent Wikipedia entries.