Ohio State University
Ohio State University: Electronegativity & Bond Polarity
Excellent graphics help this page explain the relationship between electronegativity and bond polarity.
Other
Personal Site: Covalent Bonding Single Bonds
This site is a personal site that gives "a simple view of covalent bonding" including explanations, diagrams, and examples.
Frostburg State University
General Chemistry: Why Oh, Nh, and Fh Bonds Are Polar
Frostburg State University provides a brief explanation to the question of why small hydrogen molecules, such as OH, NH, and FH, are very polar.
Other
University of Texas Dallas: Electron Appetites
The first section of this lecture on polarity and electronegativity discusses what polar covalent bonds are by using carbon dioxide as an example.