Dr Data's Blog – I love discovering new blogs, and this one's a gem. The State of Data posts are especially useful, with a lot of intriguing resources like csvkit.
TempoDB – Dealing with time series data at scale is a real pain, so I was pleased to run across this Techstars graduate. It's a database-as-a-service optimized for massive sets of time series data,behind a simple and modern REST/JSON API. We're generating so many streams of data from sensors and logs, the world needs something like this, as evidenced by the customers they're signing up, and I'm excited to follow their progress.
Foodborne Outbreaks – Unappetizing they may be, but this collection of food-poisoning cases is crying out to be visualized. (via Joe Adler)
Scalding – Another creation of the Cambrian Explosion of data tools, this Scala API for Cascading looks like it's informed by a lot of experience in the trenches at Twitter.
How to create a visualization – In a post on the O'Reilly blog I lay out how I tackle building a new visualization from scratch.
Pete Warden's blog 