Wal*Mart, Lowes, Home Depot, Selected Dennies,Selected Old Country Buffet, Selectd independnt restaurants, Applebees McDonalds, Burgr King and so many more that I can not even begain to list 'em all now offer free wi-fi at least at selected stors.
HOWEVER the more popular ones are hacker heaven..A Hacker takes out the store's router (Basically shuts it off)then sets his own "Look-a-like" router and captures all your log in info...
To date I have not had it happen to me.. But I read about it in many places INCLUDING RV FORUMS from folks who have had it happen..
I run decent security..I'm not sure it is that good however.