What a wonderful surprise for you, isewnbake! And how clever of that seed to sprout where it could grow up the fence and not be in the way.

Snapfish won't let me see more than one thumbnail unless I join.

However, the mention of a white blossom means you have some sort of Lagenaria siceraria; they are the type of gourds known as hardshell gourds. (Some other gourds belong to a different species, Cucurbita pepo, where you will also find cucumbers, acorn squash, field pumpkins, etc.)

The Lagenaria siceraria gourds bloom at night and are pollinated by moths (including the moths that become tomato hornworms, so watch out if you're growing tomatoes in your plot). Their origin is Africa and Madagascar, though they spread to India, Europe, and parts of the Americas many hundreds or thousands of years ago.

The long snakey gourd in the photo could be -- guess what? -- a snake gourd! They're edible when young. It might also be a club gourd (AFAIK not edible) or a zucca melon (edible). I believe there are other edible gourds with that shape which are not well-known in the West. But mind you, I am not promising yours is edible.

Some info about hardshell gourds, when to harvest them, and what to do after that:
http://edis.ifas.ufl.edu/mv069
http://www.benjaminslanding.com/gourds.asp

Be sure and save seeds.