Scholastic
Scholastic: Dirtmeister's Science Lab: Weather or Not
Simple experiments for exploring clouds and cloud formation. You'll find out whether dust in the air helps cloud formation and discuss how dust helps meteorologists make weather predictions.
University Corporation for Atmospheric Research
Ucar: Web Weather for Kids: Create a Portable Cloud
Using six common objects you can make a portable cloud. Get all the directions you need at this site.
NOAA
Noaa: National Weather Service: Cloud in a Jar With Calvin
This resource has all the instructions you need to create your own cloud. Pictures of the process are also provided.