24 Season 8 Episode 23 (24 s08e23) with title “Day 8: 2:00P.M. – 3:00P.M.” airs on Monday, May 24th 2010 at 08:00 pm via FOX.
Here is summary for 24 Season 8 Episode 23 (Finale) :

President Taylor focuses on the peace treaty to the exclusion of all else. Meanwhile, Jack takes matters into his own hands. Elsewhere Eriq La Salle guest stars as the UN Secretary General.

Few hours after original series aired on TV, online streaming video for 24 Season 8 Episode 23 usually available on Net and of course, if video available, as soon as possible will show you where you can watch this episode for free.