These are the top blogs I follow in the data visualization space:

http://www.edwardtufte.com/tufte/

http://visual.ly/

http://www.thefunctionalart.com/

http://hbr.org/special-collections/insight/visualizing-data

http://chartporn.org/

http://www.excelcharts.com/blog/posts/

http://flowingdata.com/

http://datavisualization.ch/

http://visualization.geblogs.com/

No matter how the tools change with time, I am able to keep up to date with the field.