I recently had an opportunity to work on a relatively high-profile project with a crazy timeline. A coworker and I spoke with the client for the first time around lunchtime on a Friday, and the client needed a completed website, complete with a relatively sophisticated design (which had, at that moment, not yet been delivered by the designer) and a relatively sophisticated data model, by mid-day the coming Monday. That's 72 hours to build and skin a fully functioning website.
I realize that "fully functioning" doesn't tell you much about the scope of the project, but we live in a world of non-disclosure agreements. Suffice to say, it was a non-trivial amount of work.
Keeping in mind that the two of us had already worked 36 hours of our 40-hour work week on other projects, we agreed to take on the project. Between the two of us we worked about 60 hours that weekend, most of it solo, and had the site finished at start of business Monday morning. This might not seem particularly heroic (particular to anyone who writes software for the game industry), but keep in mind that at Pivotal we believe strongly in the concept of sustainable pace; we really do work eight hour days, five days a week. People working late at Pivotal is relatively unusual; people working weekends is almost unheard of.