A couples of evenings ago at I had to drive through a nicely populated area just outside Brussels. I wanted to see for my self what my build-in WiFi could find. I used netstumbler to see what was in the air.
I've found 1228 WiFi connections of which were 349 wide open with no form of protection. I looked at netstumbler and it picked up more signals each time I approached the center of a town. It is probably correct to say that there are more chances to find concentrations of networks in towncenters but I have to tell you as well that you drive slower so the laptop had more time to pickup signals.
In the 1228 WiFi connections there were 8 peer-to-peer connections of only 1 had a form of protection. There were 2 hpsetup, this is usually an SSID for an HP printer. One other peer-to-peer was also a printer according to the SSID.
The majority of connections were either 11 Mbps or 54 Mbps. (The maximum my card does is 54 Mbps). The brands I encountered were 3Com, Apple, bbox2 (Belgacom), Belkin, D-link, Hercules, Philips, Linksys, Mobistar, Netgear, Sagem, Thomson, Sweex, Topcom, US Robotics, ZyXel, Nokia.