While many of the motels in the area provide internet to their patrons, the WiFi locations listed here are limited to those other than motels. These "public" WiFi Hotspots in Mariposa can be found at:

Pony Expresso Coffee Shop, on 5th Street and just one block off of Highway 140 (behind the Pizza Factory.)
FREE internet surfing to everyone.

Happy Burger Diner, located at the corner of Highway 140 and 12th Streets.
Free surfing to Sierra Tel Internet (STI) subscribers only. Non-STI subscribers must pay $2.95 per hour, $7.95 per day, $14.95 per week, or $24.95 per month.

Both hot spots are Wi-Fi and 802.11b compliant.