Put a CD player in the garden and play soothing music and make sure there is a boy cantaloupe close by...

JK...The real answer is ....Be patient....

Do you have enough bees or other insects around to pollinate your cantaloupes ? If not, you may need to pollinate by hand.

Read the following 3 FAQ's from the vegetable garden forum frequently asked questions section ...
http://faq.gardenweb.com/faq/cornucop/
- - How Do I Pollinate My Plants by Hand?
- - Squash/cucumber/melon flower: male vs. female
- - My squash/cukes/melons are not fruiting!

These websites have some pictures of male vs. female flowers ...
Watermelon - http://gardeningwithwilson.com/2008/09/24/wonder-wha-watermelon-flowers-look-like/
Pumpkin - http://gardeningwithwilson.com/2008/04/22/pollinating-pumpkin-flowers/
Cucumber - http://gardeningwithwilson.com/2008/02/23/pollinating-cucumber-flowers/
Cantaloupe (Muskmelon) - http://www.hort.purdue.edu/ext/senior/vegetabl/muskmel4.htm
Yellow Squash (male on left, female on right) - {{gwi:69811}}
Zucchini Squash - http://santarosa.ifas.ufl.edu/hot_topic_five.shtml
Winter Squash - http://www.mobot.org/gardeninghelp/plantfinder/sshow.asp?ssid=2&slddtl=1