For examples of the usage of specific verbs, online dictionaries such as Dictionary.com provide example sentences. General examples of verb usage, on the other hand, can be found in many online grammar lessons, such as those at Purdue University Online Writing Lab or on Lesson Tutor.
When searching for a specific verb on Dictionary.com, as of February 2015, the section called "Examples from the web" gives two or three sentence examples using the verb. Another way to find examples of a specific verb is to use a search engine, such as by typing "examples of 'eat' in a sentence" into Google.
For general examples of verbs used in sentences, the "Verb Usage : Tense and Conjugation" page at Lesson Tutor offers a long list of verbs with multiple conjugations, as well as a verb exercise with answer sheet. The "Making Subjects and Verbs Agree" lesson on Purdue University Online Writing Lab also includes a number of examples.