From blogger Sue Waltemath:
Squash blossomThis morning while surveying the Ponderosa I had the opportunity to get some great pictures of some squash blossoms on a hubbard squash plant which is planted in a container on the deck. Squash plants have separate male and female flowers on the same plant. The scientific word for this is "monoecious".
Squash It's pretty easy to identify male and female flowers. The female flower has a mini version of the eventual squash, the male does not. No baby=male flower. Male flowers usually bloom first so don't be alarmed when you get a lot of blooms early in the season and no fruit.

Male and Female Squash Blossoms
A more scientific source of information on the sex life of squash can be found at Organic Gardening's site "OG's test gardens squash in bloom.mht".
Great photos
What great photos of male and female squash blossoms!
Chelsey