Social psychologist Elizabeth Dunn's new study (doc) explains the right ways to buy happiness. Big Questions online has highlights. One tip is to "buy many small pleasures instead of few big ones":
If we inevitably adapt to the greatest delights that money can buy, than it may be better to indulge in a variety of frequent, small pleasuresdouble lattes, uptown pedicures, and high thread-count socksrather than pouring money into large purchases, such as sports cars, dream vacations, and front-row concert tickets.