UPDATE 8/5/12 at 3:33 A.M. Manila time: Based on the pictures on this blog post as well as other sources, Dr. Quirino Sugon of Manila Observatory, blogger at the Monk's Hobbit, has made an initial estimate of the crowd as having been at 60,000.
And the pro-RH spin machine goes into high gear!
As for the Philippine Star, it counted "more than 10,000" at the rally.
However, the pictures tell a different story.
From the UST Varsitarian:
From a friend, Ms. Anna Cosio;
From Ricardo Boncan:
And from Lenard Berba comes this picture taken earlier in the rally, with a nice view of the streamers on a footbridge: