Simple quotation mark rules for usage in American English are available on ThePunctuationGuide.com. The rules are divided into simple categories and aided with usage examples.
The Punctuation Guide goes over the basic rules for using quotation marks with other punctuation, using quotation marks for direct quotes from the words of others, and using quotation marks in other unique situations, such as for measurements, translations, nicknames, and writing about letters or words. Each section of The Punctuation Guide's quotation mark page briefly describes the correct usage then provides one or two examples of the correct usage. The quotation mark is also explicitly related to other punctuation, and links to basic rules about other punctation are provided at the top of the page.