What is your favorite data visualization blog? What is the best blog on data visualization?
I'm making this question a community wiki since it is highly subjective.  Please limit each answer to one link.

Please note the following criteria for proposed answers: 

[A]cceptable answers to questions like this ...need to supply adequate descriptions and reasoned justification. A mere hyperlink doesn't do it. ...[A]ny future replies [must] meet ...[these] standards; otherwise, they will be deleted without further comment. 

 A: Junk Charts is always interesting and thought-provoking, usually providing both criticism of visualizations in the popular media and suggestions for improvements.
A: It's not a blog, but Edward Tufte has an interesting forum on information design including data visualization.
A: EagerEyes  by Robert Kosara (~5 posts a month). This blog includes tutorials and discussion articles plus it has a great home page with lots of links to useful information.
A: https://web.archive.org/web/20120102041205/https://datavisualization.ch/
by Benjamin Wiederkehr and others (~15 links a month). If you want heaps of links you can subscribe to their twitter feed twitter slash datavis (~5 links a day)
ahhh... i'm a new member and so i can only post one link per post.
A: Chart Porn
I find the blog name pretty humorous. Great dataviz.
A: Andrew Gelman doesn't limit himself to visualization, but he comments on it frequently.  
Statistical Modeling, Causal Inference, and Social Science
A: Check out the data visualization blog from Visual.ly.
A: I see all my favorite blogs have been listed. So I'll give you this one:
I Love Charts
It's a bit light hearted.
A: Light-hearted: Indexed
Also, see older visualizations from the same creator at the original Indexed Blog.
A: Dataspora, a data science blog.
A: I can't pick just one :)
Check out this great blog post by flowingdata: 37 Data-ish blogs you should know about
A: FlowingData | Data Visualization, Infographics, and Statistics
A: Information Is Beautiful | Ideas, issues, knowledge, data - visualized!
A: information aesthetics - Data Visualization & Information Design
A: We Love Datavis, a data visualization tumblog.
A: 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.
A: A daily dataviz feed for/by data nerds.
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