Easily one of the most addictive websites ever, TV Tropes is a website dedicated to cataloguing the tricks of the trade of writing fiction. If you've ever had a conversation that included, "You ever notice how in movies..." or "It seems like in every book I read...", then you're discussing tropes.
Tropes are tools; they are not inherently good nor bad, and their success depends on how they are used. The website includes a massive trove of pages about tropes, as well as pages for individual works of fiction and the tropes they include. Odds are, your favorite book or movie has a page, as the site is very well-maintained.
Trust me, it's better than it sounds. If you, like me, ingest a lost of fiction, you'll be hooked as you read about trope after trope that you've seen a thousand times before but haven't noticed. It's one of the best ways to ruin your life.