Ok so I am being sad today. My router gives me pretty graphs showing my daily and monthly incoming and outgoing traffic.
Here are some examples of what it tells me
Jan in 1587MB out 240MB
Dec in 8907MB out 486MB
Aug in 43159MB out 10176MB
Its a good job I am not on a 3G dongle
August 23rd was a busy day with incoming of 23512MB and outgoing of 569MB. I would guess thats when I was downloading Windows password cracking rainbow tables