Also, I enjoy this site http://flowingdata.com.
http://www.amazon.com/Visualizing-Data-William-S-Cleveland/d...
There are some frustrating typos in the code, but if you're a programmer you should be able to fix them quickly, and you build some neat stuff.
Cleveland worked at Bell Labs and his work is timeless and very practical. It isn't about artwork or making things look nice. It's about communicating information. I like to contrast his work with Tufte's. Tufte comes up with some nice stuff but I find it to be more art than science where the information is clearly sacrificed to ascetics. With visualizations I always ask myself, "Do you know more now about what is going on than you did before or is it just something nice to look at?" Way too often it's the latter.
[1] https://www.amazon.com/Elements-Graphing-Data-William-Clevel...
[2] https://www.amazon.com/Visualizing-Data-William-S-Cleveland/...