I think PC Pus this month (could have been a newspaper) mentions public wifi points. Some that you see advertised are actually not airport owned and genuine but are actually fake sites. They will probable work but . . .
Now
www.poihandler.com lists wifi access points by country. Many of these are legitmately available, like PC World, but I don't know if these are free or publicly available.
You could use their listing either for pre-journey research or use a SatNav and do a POI search.
I have just done this on my PDA, I have 9 pubs and bars listed at UK Hot Spots within 5 miles. Under Unofficial Free WiFi Internet Access I have none with 25 miles and only 3 in UK. Draw your own conclusions.