The Office Season 6 Episode 25 (The Office s06e25) with title “Whistleblower” airs on Thursday, May 20th 2010 at 09:00 pm via NBC.
Here is summary for The Office Season 6 Episode 25 :

In the Season 6 finale, the heat is on when the media discover that Sabre’s printers catch on fire. When Sabre CEO Jo Bennett (Starring by : Kathy Bates) arrives to unmask the whistle-blower, the staffers point accusatory fingers at Andy, who passionately denies that he’s the leak.

Few hours after original series aired on TV, online streaming video for The Office Season 6 Episode 25 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.