Elderhostel offers an international program of classes and seminars for people over 60. (Spouses under 60 and companions over 50 are welcome too.) You can study aborigine culture in Australia, barns of Vermont, dance, religion . . . it’s an impressive and ever-changing list. The prices are low and may include travel fare, room and board. Scholarships are available. The catalog is exuberant, and the people involved seem to share that feeling. We hear 100 percent good news about Elderhostel, both from