I recently got my Raspberry Pi after five months on the waiting list. I was running it headless via ssh, but I wanted to know its networking speed. After a bit a googling, I found "tespeed", a command line interface to the actual speedtest.net servers:
https://github.com/Janhouse/tespeed
It worked nicely, and I also started measuring the speeds of my various linux lowendboxen. It works very nicely after adding the python-lxml module to stock Python on debian installations. It's interesting to watch speedtest.net increase the transfer size by a factor of two at each stage.