You might experience something like the following:
24 hours: Mild delirium, mood swings, and periods of intense sleepiness or activity.
48 hours: Impaired coordination, hormonal changes, and decreased general memory function, but improved short-term memory.
72 hours: Visual hallucinations and unintentional periods of "microsleep" and black out.
100+ hours:Re-enactment of the cult-status movie, Fight Club.
11+ days:Win the prize for longest period a human has voluntarily gone without sleep (current holder is one Randy Gardner from San Diego, California).
2+ weeks: Some chance of death. Experiments with rats revealed that they died after 2-4 weeks (probably from hypermetabolism) after researchers kept them awake in an experimental setting.
6+ months:Certain death; If not death, then onset of rare disorders like Fatal familial insomnia.