Taking a kind of if-you-can't-beat-'em-join-'em stance, NBC, which like all of the other networks, has battled the YouTube video website over users posting segments of its shows online, said today (Tuesday) that it plans to promote its fall lineup via the website, providing clips from such shows as The Office, Saturday Night Live and The Tonight Show with Jay Leno. It also plans to buy ads on the site and mention YouTube on the air.