Being a visual arts major (illustration, specifically), I decided to look at concept art blogs, which comes as no surprise to anybody, at all, ever.
Concept art is a vital part of creating the worlds we see depicted on screen in film, games, and other visual media; it's the canvas upon which that created world is built upon, whether it involves a Tolkien-themed fantastical approach, or giant robots punching sea aliens repeatedly in the face. Much of its goal is to finalize character design and concept, which is usually most important in a production which relies on a sympathetic—or at least relatable—protagonist. Location concepts are also a big factor, especially if it's a big fantastical production, or a sci-fi epic, or whatever you like. Even in garden variety films or games that take place in a world very similar to ours, everything must be designed and finalized, and that begins with concepts from the art department.
Also, generally, concept art blogs? Not a whole lot of writing. Mostly just art. (Sorry.)
The first blog I stumbled across, The CAB (Concept Art Blog), was in Portuguese. My limited understanding of the language doesn't negate the cohesive design and presentation, though; even if you aren't a Portuguese-speaker, it's easy to navigate. I spent about ten minutes scrolling through the site with an unholy amount of delight. Excellent composition, and what looks like comprehensive notations on each piece, or pieces. I liked it.
Next stop was Concept Art World, another excellent site with pleasing visuals. Usually when you're dealing with artists, you're dealing with a very well put-together website. We're big into the whole Pretty Thing; it distracts from our chronic inability to write anything in-depth about what we create. It helps that the blogs I've been visiting are Grade-A Professional, and not as personal or informal as I should probably be looking for, but there are few informal blogs that comment on concept art as a whole, rather than the art created by the individual themselves. This site is good. All-encompassing. Again, I liked it.
Lastly, we've got Fuck Yeah Concept Art, which, again, easy on the writing, but altogether a great resource for people interested in the entire idea of concept art. There are links to articles, and you can search by tag (always a helpful feature) and there's a focus on the artists featured, rather than just their work. Unlike the previous blogs, the design leaves something to be desired, as the platform (Tumblr) follows set templates, much like Blogger.
Out of the three, I'd visit Concept Art World a bit more frequently than the other two. A) I can understand it, and 2) It's shiny. All three of them are great for the concept art connoisseur, but I think CAW is most appealing to me as a resource.