Ask Mr. Smarty Plants

First of all, squash plants are monoecious (male and female reproductive parts on the same plant but in separate flowers).  The male flowers tend to occur near the center of the plant and the female flowers usually occur nearer the outside.  You can see in the photograph that the female flower has a swelling at the bottom, the ovary, that will become the squash fruit if it is pollinated.  The male flowers tend to appear and open earlier than (sometimes several days before) the female flowers.  They open early in the morning and then die and fall off.  More male blossoms will replace them and female flowers will also eventually bloom.  In order for there to be a fruit, the female flower has to be pollinated by the pollen from a male flower.  This is normally accomplished by an insect first visiting a male flower for its nectar, collecting pollen on its body, and then visiting the female flower for its nectar and shedding the pollen on the pistil of the female flower.  So, your lack of fruit may be that: 1) all the flowers so far have been male flowers and you should soon get female flowers as well; or 2) the pollinator population in your area is reduced (see the information on honeybee decline).  If you see that your plant has both male and female flowers but you're still not getting fruit, you can assume that for some reason your female flowers are not getting pollinated.  You can do the pollinating yourself by taking a small artist's brush and collecting pollen from the stamens of male blossoms and then brushing it onto the pistils of female flowers.  Brushing the pistils with pollen from several male flowers should do the trick.