Disclaimer: Do not enter this site unless you have about an eternity of free time. In other cases it will ruin your life.
TV Tropes started in the year 2004 focusing on extracting and listing tropes from TV series (most notably Buffy The Vampire Slayer) and films and throughout 7 years it emerged to being one of the biggest encyclopaedia on media.
What is great about it?
It is an enormous almost unlimited source of information on tropes, motifs etc. Ranging from western animation, anime, comic books, fan fics, films, literature to music and sound effect, new media, print media, radio, sequential art, tabletop games, television, theatre, videogames, webcomics (this is just categorized under “media”). Of course it is not formal like some other wiki which name I won’t tell ;) TV Tropes takes what is best from collective knowledge of Net surfers. In addition not only does it function as an encyclopaedia but also as a forum for loads of fans, who are discussing whether trope should be put on the page and listed in some of the works there. Even though TV Tropes unfortunately cannot be perceived as an academic source it can still help you when writing your degree paper etc. E.g. I couldn’t find a book which would list any kind of Death representation in English literature. But when I entered TV Tropes, typed “Grim Reaper” in the search box soon I was browsing through literature subcategory on the Grim Reaper. With no doubt it is helpful. However there is one observed downside of using TV Tropes. When I started reading it I stopped after 3 hours! Time passes by so fast when you browsing through it. Moreover sometimes fans of one or another creative work think too highly of things they praise so better be on a lookout for them. It sometimes lacks the eye of the critic :D
Nevertheless TV Tropes is a great site containing much more useful information than any other online or printed encyclopaedia ever.
Final score 8/10