That's too bad that the car rental guy said that. But some ideas...
* If you're a gambler, across the highway from the airport is the Oneida Casino, with all of the requisite gambling, buffet, bingo, slots, etc.
* For history buffs, particularly WWII buffs, try the National Railroad Museum. A wide variety of trains, including Gen. Eisenhower's command train from WWII.
* Part 2 for history is Heritage Hill State Park. It's a cultural museum/park about the history of the region.
* If the weather stays nice (it was close to 80 here today), and you want some fresh air, try the Bay Beach Wildlife Sanctuary. Lots of trails, rescued animals - sort of a minizoo. You can feed the geese. A nice place to the take the kids.
* There's a mall about 2 miles south of the Resch Center called Bay Park Square, but the better shopping experience is Fox River Mall about 35 minutes down the freeway in Appleton.
Try greenbay.com for more infomation on attractions, events, and so on.