For what seems like my entire life, NBC has used the same Wagnerian piece of John Williams' music for all of its Olympics bumpers and promos. I couldn't find any of the NBC Beijing promos on YouTube, but I did manage to track down the promo spots used by BBC Sport and France2, who air the Olympic Games in the U.K. and France, respectively. I find the contrast between the three nations' presentations quite curious.

From France2:

From BBC Sport:

If I can find a decent recording of NBC's material, I'll append it.