I only recent became aware of the chartsnthings blog, which is about (direct quote from site);
A (personal) blog of data sketches from the New York Times Graphics Department.
I believe I follow most of the blogs listed here so far in my feed reader, and this one is a bit different. It is more of a behind the scenes look at the development of the NYT Graphics department, whom produce a wide array of excellent graphics (in a wide array of mediums) for the New York Times. Just those related articles should be followed, and are frequently mentioned in the other "discussion" sections of blogs like flowingdata or chartporn.
It is different because it describes some of the workflow of developing graphics, including initial brainstorming ideas (including ones that don't pan out). And it is certainly interesting to see the developmental stages and reasoning behind certain graphical choices. Note it isn't an instructional blog. They don't provide code R or Flash to replicate graphics, they don't give tutorials on how to use Illustrator.