University of Victoria (Canada)
Study Zone: Parts of Speech
Nice brief visual summary of the parts of speech - clear and concise - followed by an interactive practice quiz to reinforce concepts - great for ELL - has links to more in-depth explanations.
University of Ottawa (Canada)
University of Ottawa, Canada: The Parts of Speech
This site offers concise explanations of all the parts of speech in English, with plenty of examples to aid understanding.
Other
Schoolhouse Rock: Interjections!
This site from Schoolhouse Rock provides the lyrics for the grammar rock song about interjections. This old song will help you remember what interjections are and how they work. It is taken from the old cartoon series, Schoolhouse Rock.
English Club
English Club: Learn English: Vocabulary: Word Classes and Word Forms
Links to information on different word forms including verbs, nouns, adjectives, adverbs, prepositions, interjections, prefixes, suffixes, contractions, and "wh" question words.
English Club
English Club: Learn English: Vocabulary: Word of the Day
Links to seventeen different word lists under the following categories: common words, verbs, nouns, adjectives, adverbs, prepositions, and interjections.