Scribd: 5M daily uniques
Justin.tv: 3M daily uniques
last.fm: 2M daily uniques
It might be satisfying to include some reference lines on your daily user graph, so you can celebrate when you serve more pages than, say, McDonald's sells fish sandwiches, or Wal-Mart sells Spiderman action figures, or whatever.
Of course, this is a meaningless comparison, because the number of people that Scribd or Justin.TV reach on a daily basis is more closely correlated to the number of users they have than the number of customers.