As my ISP only updates its usage webpage once a day at ~3am, I thought I'd build my own real-time one.
It's connected to my Linux box via the parallel port and is controlled by my 'lcdd' (LCD Daemon).
It allows messages to be sent to the display via UDP or FIFO (eg: syslog, as you can see).
The usage is reported by a cron job that queries my router stats every 5 minutes.
View the video of it in action!