So I thought I'd contribute some ideas myself, in the hopes of helping someone (a reader or writer) who needs new ideas for blog posts. Here are some of the posts I've done that I think are relatively original and may spark some ideas for you!
Examples: In Twilight's Defense
Why I Admire Steven Moffat
Why I Hate James Patterson / What We Can Learn from James Patterson
2) List some cliches that you hate.
Examples: Tropes That I Despise
3) Write about your favorite authors.
Examples: What My Writing Idols Teach Me
Writing Advice From the Outside
Biographies of Authors
An Open Letter to J.K. Rowling
People Who Inspire Me
Examples: Thoughts on Healthy Relationships in YA Lit
Exploring Family in YA Literature
5) Make a wishlist to post on your blog.
Examples: My Fandom Wishlist
Stuff on My Wishlist Right Now
6) Put together an itinerary for a "literary" vacation.
Examples: My Ideal Literary Trip to Britain
7) Don't forget the classics, like bookcase tours and book haul posts!
Examples: Tour of My Bookshelf / Video: An Updated Bookshelf Tour
8) Analyze a literary technique using a famous movie/TV show.
Examples: SHERLOCK! or How POV Affects Readers
Inception's Lesson for Novelists
9) Talk about bookish mistakes you've made and issues you've changed your mind on.
Examples: Changed Perspectives: Self-Publishing
Book Snobbery: A True Story
10) Write a post from the perspective of a/your fictional character.
Examples: Facebook Song Game, feat. Sage O'Riley / Facebook Song Game, feat. Suzanne Clever
Sage O'Riley: How to Deal with Stupid Authors / Mandy Gale: Stereotypes
Why My Book Characters Don't Mingle
11) Discuss how your other interests play into your interest in books/writing.
Examples: TCWT Blog Post: Joys of Music
How My Interests Help My Writing
12) Examine the educational system, which is highly related to the literary world.
Examples: Thoughts on Reading in School
Writerly Things They Don't Teach in School
Teachers I've Hated and Loved
BONUS: Try out some of the post types I use on a regular basis: music posts, book recommendation posts, "on this day in my history", Wordy Wednesday/Short Story Saturday, monthly humor posts, "taking stock", and Pinterest roundups!
Use one of these ideas? Link me! Got another idea? Tell me!