NeoK12 English Grammar videos is a series of videos to help students better understand parts of speech such as verbs, adjectives and prepositions, as well as more advanced concepts such as tenses, subjective complements, past particples, gerunds and gerund phrases, infinitive phrases, nominal phrases, indirect objects and objective complements.  All videos and lessons on this site have been reviewed by K-12 teachers and are safe for kids.

This sit has interactives to help kids learn about and practice different types of nouns, adjectives, eponyms and idioms. The site also has a timeline of the origins of the English language, as well as a game exploring the origins of many English words.

From site:  Our friends, the Grammar Gorillas, need help identifying parts of speech. If you click on the right word in the sentence, our friends get a banana. And you know, a gorilla with a banana is a gorilla with appeal.

Beginner (nouns and verbs only)
Advanced (all parts of speech)

This activity is no longer available online.  As an alternative, take a look at Grammar Monster.

Designed for kids in grades 2, 3, 4, and 5, Grammar Blast provides a group of multiple-choice quizzes where students answer questions on sentence structure, nouns, pronouns, verbs, adjectives, adverbs, capitalization, punctuation, and prepositions.  Each unit has 10 questions and kids earn up to 100 points.

For more grammar games and lessons, look at the complete list of Grammar Websites

These 20 brief webcasts help students analyze some of the more complex parts of English speech.  These include: verb tenses — past perfect, past perfect and present and past simple and perfect; modal verbs, gerunds, infinitives and passives; first, second and third conditionals, mixed conditionals; reported statements, questions and verbs; and making comparisons.