Internet radio listeners are worried their Web sites will be shut down by rate hikes, which will take effect later this summer. But this summer is expected to be great for business for a different kind of Web site: Gasbuddy.com. As gasoline prices rise, and the summer driving season gets going, that site is getting more and more hits. Drivers enter their zip code, and get a list of gas stations with the lowest prices in the area. Gaspricewatch.com offers a similar service. But these sites rely on a rather low-tech tool: volunteer activists who monitor local gas prices. In Gasbuddy lingo, they're known as "spotters."