I just bumped into this blog from a team at SNAP, where Matthew Leonawicz and his colleagues share some great data visualizations they've been creating with R (and some code snippets). Here are two nice examples of geographic networks on a flat map and on a 3D model of the Earth.
This is very similar to the work of James Cheshire (UCL) on mapping the World’s Biggest Airlines, global migration and commuting patterns. Neat stuff. I've just added their blog to my feedly.
[image credit: Matthew Leonawicz]