The website I frequent the most and educates me daily is Answers.com . Let me count the "why"s:
--When I encounter a puzzled word during my online reading, it gives me the correct pronunciation right away plus translations in various languages.
--The translation into Chinese is especially useful. I can cross-reference the meaning since I relate to my native language better.
--The site gathers different editions of encyclopedia for the searched word in one place.
Now, prepare a pot of tea and see it for youself. Search the word "tea" at the site. When you are at the tea (tree) page, first take a quick glance of the page from top to the bottom before reading any part of it. See how much knowledge it contains? Enjoy and explore. :))