I read a large number of comic book/superhero blogs. Covering them here is a little tricky, because, with a few exceptions, they're similar in tone and there is quite a bit of overlap in material , and without checking, I wouldn't be able to tell you if a post came from Comics Alliance or ComicVine Site Mashup.
This is large enough to split into two parts.
13th Dimension, Comics, Creators, Culture: This is my most recent addition to my reading list. Another comics blog linked to it and I added it to my list. A good mix of commentary, interviews and reviews.
Again With the Comics: A solid blog, mostly commentary, that seems to be dead. It's one of those zombie feeds that hung around as I moved from reader to reader. Which is a shame, because I really enjoyed the writing.
Bully Says: Comics Oughta Be Fun!: A fun mix of comic history and oddball features. (365 days of Kirby tech, 365 Days of DC House Ads) Just a fun site.
Comic Coverage: Another dead blog, though it's fun to swim in the archives.
Comics Alliance: Mainstream comics coverage. It's probably redundant, in that looking at the posts here, I don't see anything not covered by another feed,
Comics Are Awesome: Infrequently updated, lists and mini reviews.
Comics Should Be Good! @ Comic Book Resources: Another blog with reviews and commentaries, though with a tighter theme than most sites.
ComicVine Site Mashup: Good features marred by their terrible reviews. In particular, they love, Love, LOVE Tom Taylor's Injustice. I've never seen such effusive praise for such mediocrity since this quote about George W. Bush early in his presidency. "It must be very strange to be President Bush. A man of extraordinary vision and brilliance approaching to genius, he can’t get anyone to notice. He is like a great painter or musician who is ahead of his time, and who unveils one masterpiece after another to a reception that, when not bored, is hostile." I'd say that there should be some kind of disclaimer that that tells the reader that Tom Taylor is writing these reviews, except, that even though these puff pieces are the journalistic equivalent of a dog humping your leg, they're still many times better than Taylor's work on Injustice, and are therefore are unlikely to have been actually written by him.
DC Women Kicking Ass: Characterized by a large number of short posts. As the title suggests, it's about DC Comics women kicking ass and being awesome. A bit heavier on the Bat Family books than my personal preference, but always solid and not infrequently outstanding.
Dispatches From The Fridge: Le Sigh. Another dead blog.
Every Day Is Like Wednesday: Another site of reviews and commentary. While it covers much of the same material in the rest of the feed, it's very accessible and engaging. If I only read one review of a given comic, I would tend to prefer this sites.
Get-a-Life Boy's LSH Blog: Not dead, but sleeping, hopefully. A blog dedicated to chronicling the appearances of the Legion of Super-Heroes in a given week's comics. Since there are currently no Legion books being published, there is nothing to write about.
Gone & Forgotten: The first comics site I started following. Like a lot of people, I first heard about it when it was featured on National Public Radio's This American Life. It's switched locations a couple time, laid fallow for years and, in general, has died and been reborn more times than Jean Grey. As the title suggests, it's a site that looks at terrible comics and characters that are best forgotten, though it doesn't adhere to that theme as tightly as it did in the earlier days. It's updated with some frequency these days and definitely worth looking at.
Henchman Publishing: I see this blog moved in 2012. Good to know.
Jim Shooter: From the legendary editor himself. It was briefly very active in 2012, and now seems mostly dead. I really enjoyed it. Shooter has a writing style that really appeals to me, and his behind the scenes reminisces were really a lot of fun to read. I hope he returns to the blog someday.