Capital Community College Foundation
Guide to Grammar and Writing: The Question Mark
This site from the Capital Community College contains information regarding the correct and incorrect usage of the question mark. Includes some examples.
University of Calgary
Univ. Of Calgary: Punctuation Rules Question Marks
A good resource detailing the rules, uses, and misuses of the question mark in English punctuation. Includes examples and a quiz.
Other
Kim's Korner: Punctuation Rules: Question Mark
A single rule is given for question mark usage in sentences along with an example.