Armed with little more than a couple of coordinates and a GPS device, Melanie Murray hits the trail with her miniature pinscher, Peanut Butter, every spare chance she gets, searching across New England for packages known as “geocaches.”

What began around 2000 as a hobby for GPS enthusiasts who hid and hunted for a handful of caches across the country has now grown into an online community with more than 800,000 active geocaches hidden world wide, according to Murray. The rules are simple: pull the coordinates off of the official geocaching Web site, locate the cache – which is a hidden item that can be as small as a fingernail or as large as an old army ammo box – record the find on a logbook kept inside the cache as well as online, and then move on to the next one.

Though they range in theme, content, location and ease of finding, Murray said tracking down the geocaches is all about the thrill of the hunt. To date, she has found more than 2,000 of them and spent countless hours over the past three years slogging through snow, wading through streams and crawling over boulders in the Northeast.

“You find all kinds of interesting things and meet different people. The only investment you have to make is buying a GPS,” said Murray. “(After you find a geocache) you go online and log the find and see what other people have written about it. I’m totally addicted. Anytime my husband is working or going fishing, I’m out geocaching, even in the rain, sleet and snow.”

Murray, who works in Salem’s finance department, first learned about geocaching from Fire Chief Kevin Breen in the fall of 2006. Breen, who has around 500 finds to his name, stumbled across the activity after he accidentally found a geocache while vacationing on Cape Cod. A few months later he convinced Murray to go along with him and try to find a geocache hidden at the town’s old fire station and hose house on Bridge Street.

“It takes a couple of times to catch on and comprehend it,” Murray said, recalling that she did not even have a GPS unit with her that first time. “It’s just something that you can do by yourself. You can do it anytime, day or night, and it’s good exercise.”

Geocaching has also helped Murray find public conservation land and hiking or walking trails close to home that she would have otherwise never known about, like the rail trail in nearby Windham or a wooded spot with a great view overlooking Moeckel Pond.

The online community that has built up around the activity – Murray described it as similar to Myspace or Facebook – has also kept her entertained.

Murray said the other geocaching enthusiasts who follow her trips know her for the wacky adventures she has while on the hunt – like the time she passed a naked man who had very clearly been skinny dipping in the abandoned quarry in the park she was hiking through.

“We’ve gotten some friends from geocaching. You’ll run into them on the trail and they’ll say, ‘Finally, I can put that profile name to a face,’” Murray said.

Murray and Breen have also put geocaching to work for the town. This past spring, recreation director Chris Dillon used geocaching to sponsor a cleanup event for the town’s Hedgehog Park. According to Breen, the geocachers who attended received credit for taking a couple of hours and clearing brush from the front of Hedgehog Pond.

“It’s a group of people who like the outdoors and who are into trail hiking and climbing. So one of the other things they promote is keeping the woods clean,” he said. “One of the things that interested me in geocaching is it doesn’t cost anything. If I go geocaching, I can preplan where I go. It’s getting out in the woods and seeing the sights. They’re located everywhere.”

For Murray, it’s all about that feeling she gets when she reaches up inside an oak tree and pulls out a hidden film canister or spots a camouflaged box sitting in the middle of an isolated stone wall.

“I’ve scraped a leg and been stung by bees. I was never used to that before,” she said. “It’s a challenge. I guess that’s what it is. It’s the challenge of finding them. I’m mostly interested in seeing how people hide them. I never tire of it.”