SUNY Empire State College
Empire State College: Apostrophes
This resource looks at the three main uses of apostrophes: to take the place of deleted letters; to show possession; and to show plurals of letters, numbers, symbols, abbreviations and words used as words.
Other
Illinois State U.: Punctuation Made Simple Apostrophes
What is an apostrophe and how is it used properly in punctuation? "Punctuation Made Simple," gives some concrete examples for apostrophe use.
Other
Sandhills Community College: The Apostrophe
A valuable resource for learning about the uses of the apostrophe in English punctuation, including apostrophes with possessive nouns as well as contractions. Provides examples.