I think the longest I've done without sleep was about 54 hours. I went from midday on Saturday through to 6pm Monday. In that whole time all my caffiene consumption was contained within 3 cups of (strong) coffee.
The basic chain of events for this was I was going to a conference.
I has to catch the train at about 6am on the Sunday, so, there was no point in me getting sleep before leaving as I would have just been even more wasted for the travelling.
From there it was about 24 hours of travelling (including waiting for connecting trains).
When I finally got to my destination at 6am on Monday I had to go to the conference which was starting around 8am.
Well, the next 8 hours were spent listening to talks with an attention span of about 5-10 seconds and the final half of that day at the conference spent blacking out
After another hour of travelling to get to my accomodation (was staying with relatives) and some time to eat, I completely crashed.
It was definately a fun bit of time, but I have no intention of repeating it again.