Come to the bay area, the Prius is everywhere.
In my neighborhood alone there are two 2004s (red and white) and a classic (tan/gold?). Go a few blocks up there is another 2004 (white), owned by the city of SF, and another classic (white) also owned by the city.
Moving along on my day I can spot them throughout the city, but the most concetrated sightings have been in the Twin Peaks, Castro / Church, and Marina districts. There are a lot more there but I don't want to count those because I don't see them regularly.
On the freeway I usually see the three same Prius, I can tell because its the same time everyday and they do little things that stand out. Two of them a silver and a white travel at around 75 mph, traffic is moving at only 80, but it still makes them stand out. The other one the silver is the opposite, he criuses along and then guns it to pass a bunch of cars and flys off into the horrizon.
There are also two more silver Prius to be seen at school, both owned by Staff. One is parked in the Faculty level of the parking lot, the other behind the Event Center (nice shortcut between a bunch of buildings).
I've seen all the colors now, blue, green, silver, white and black. The bay area is a great place to find Prii, high gas prices (2.38-2.61 for reg) and we really like our clean air.