According to the count I heard, 28 cyclists participated in the first Critical Mass event in Erie! We started at Perry Square, went around the square, and down 6th street. We returned down 10th, went down State street, and then went westward to Frontier Park along the Bayfront. Unfortunately, that was a good place for me to continue home, while the rest of the participants circled back along 6th street.
Here are the (decent) pictures I took on Flickr.
Update: 2008 Nov 1: Here's another page with a description of the event.