For parents who have difficulty occupying themselves while their children are away at camp, the Specialty Travel Index also can give some direction on adult adventures.

A sampling: hot-air ballooning, safaris, white-water trips, psychic archeological tours, European barge cruises, wagon-train trips, train ride from London to Hong Kong, opera music and genealogical tours. Or maybe you'd like to try psychoanalysis in Beverly Hills?

One listing, Sunny Rest Lodge, offers "naked lunch, and dinner, too," and describes itself as "a rustic nudist resort in the foothills of the Pocono Mountains." Suggested activities: sunbathing, volleyball, tennis and disco dancing, all au naturel.

Among the Specialty Travel Index's most intriguing offerings: "French Decadence" and "The Camptel."

"French Decadence" includes ballooning near Lake Geneva (evening gambling in Evian); cooking classes with chef Michel Guerard (of Cuisine Minceur) at his spa in the Pyrenees; a week cruising in the Loire Valley on an antique-furnished hotel boat; wine-tasting and bicycling in Alsace during harvest-time; romping on the beach in St. Tropez. Twenty-one days for $4,700, including first-class hotels, transfers, 11 gourmet meals. Contact: Return to the Earth, 320 Judah, San Francisco, Calif. 94122.

"The Camptel," located 36 miles south of Cancun, Mexico, provides "deluxe camping in furnished tents, with maid service, on remote white sand beach; coco palms and turquoise sea; gourmet meals served by candlelight in native thatch palapa; hot showers and cold drinks; no electricity, telephone, or television." What do you do all day? Snorkel, scuba-dive, beachcomb, sail, fish, explore Mayan ruins and relax. Daily rate, breakfast and dinner included: $22.75 per person, double occupancy. Camptel Ventures, Inc., P.O. Box 32794, San Jose, Calif. 95152.