Yes, in the past you could have used wireless internet at McDonalds, but unless you were using it on your Zune (thanks to a deal with Microsoft) you had to pay $2.95 for a few hours of wireless connectivity. Well now it has all changed.
Starting today, according to Reuters, McDonalds will begin offering free WiFi access in approximately 11,500 of its over 14,000 locations. That gives you an better than 80% chance that your local McDonalds has free wifi!
Check out the McDonalds location finder to see if your location has wifi.