Here are some sites to help thoroughly learn about verbs:

Quia Verb phrases-- go through 10 sentences and find the complete verb phrase
Verb Quest--This site has many links to sort through about grammar and verbs.
HyperGrammar (linking verbs)-- The student takes a simple quiz decided which verbs are linking verbs. This is from a college website
HyperGrammar (Verb Tense)-- This is a college quiz in which the student determines whether the verb is formed correctly in the sentence.
Be Verb quiz-- This is a simple fun quiz to help students learn the verb tenses of Be.