Grammarly
Grammarly Blog: Verb Forms
This page explains the five forms of verbs: root, third-person singular,present participle, past, and past participle and provides examples of each.
Capital Community College Foundation
Guide to Grammar and Writing: Possessive Forms
As you learn possessive forms, you will also learn about gerunds, present participles, compound nouns and more. This is a very complete resource tool for this subject.