The WaPo says there were anywhere from 150,000-300,000 people there. My own estimate was 200,000 because of this: When I was standing at the corner of 15th and Pennsylvania, I could see people wall-to-wall down 15th toward the Mall. That same line of people was packed shoulder-to-shoulder all along Pennsylvania Ave. in front of the White house, they turned right at 17th (I think that's the street), went one block, turned right again, and continued about 3 very long blocks, before turning right yet again on 14th street and back down toward the Mall. In other words, when I was standing at 15th and Penn. I could see a steady and unbroken line of people filling the wide downtown streets for 12-14 blocks or more, and that wasn't everyone by a long shot. Anyway, the WaPo has more coverage, some great photos, and this video. I have some more photos I'll post later but, well, the pros really do a better job than i do.