Focused primarily on fantasy and science fiction books, this blog raises overused tropes & themes that plague the genres, explaining what the issues with them are. They are alphabetically listed behind the above link.
I have to admit, some of it's hard to read, not because it's poorly written or poorly explained, but because I know I've stumbled on more than a few of those points myself.
It's also tough because it leaves one feeling like there's few options left once you've excised all these horrible pitfalls and possible writer's traps.
But it's a valuable read, I have to say, and is making me think a little more outside the box for my next work.