This was another craft we did at camp. I bought a kit from Michael's, along with extra beads, key rings and string. I was really impressed how even the younger kids (rising 3rd graders) did so well. It's one of those things that once you get it, its easy. Most of the kids made one. The snake was the easiest and most popular.
Vinyl or nylon lacing (same aisle as pony beads)
This is a great rainy day project or an activity for a long car ride. Nice hand-made gift as well. Might even be fun to do at sleep-over.