Having a PDA with WiFi built it is having the ability to surf the net on the PDA or sync it wirelessly...
Please don't confuse this with the pay internet wireless services like Blackberry or Palm. They are still too slow, at least in the States, but that will change...
WiFi is the basic 802.1a/b wireless nodes like Linksys that many of us who have more than one computer at home use in liu of stringing more cables thru the house walls.
You need a wireless router at the cable end, about 100 bucks here in the States, and wireless cards or boxes, which run about 40-60 bucks at each computer.
But many businesses who have extra bandwith are putting up nodes so their customers can surf while they enjoy the services of the business.
You can try:
http://www.shmoo.com/gawd/
for a sample search engine to find open points.
Most airlines have wireless nodes around their first class clubs.
If you know the warchalking symbols, you can also find wireless nodes on the street....