I just found an interesting R script that can visualize your email inbox.
Edit: The post has been moved to r-bloggers.com. http://www.r-bloggers.com/sna-visualising-an-email-box-with-r/ (Thanks to M Mouse for the updated link.)
The script creates a Graph using ‘from’ and ‘to’ addresses of the messages in your inbox. I din’t have to do any modification in the script, it worked directly for me in my gmail.