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 Steven Moffat is Brilliant / Steven Moffat Is Not Sexist
Why I Hate James Patterson / What We Can Learn from James Patterson
2) List some literary cliches that you hate.
Examples: TCWT Blog Chain: Good and Bad
Plot Devices I Despise
3) Write about your favorite authors -- not just their writing, but their lives too.
Examples: What My Writing Idols Teach Me
Writing Advice from the Outside
Biographies of Authors
Open Letter to J.K. Rowling
People Who Inspire Me
Examples: Thoughts on Healthy Relationships in YA Lit
Exploring Family through YA Literature
Issues of Race in YA Lit
5) Make a wishlist to post on your blog, especially a book related one.
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: An Updated Bookcase Tour / Tour of my Bookshelf
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 fictional/your fictional character.
Examples: Facebook Song Game with Sage O'Riley / Music Shuffle with Suzanne Clever
Sage O'Riley: How to Deal with Stupid Authors
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 -- it's 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 regularly use: music posts, book recommendation posts, "on this day in my history", stream of consciousness, 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!