Companion website to A Writer's Reference:

Click on "Grammar Exercises" and then select from the letter-number codes. Important: When a page pops up asking you to log in, just click "cancel" to proceed to the exercises.

To use this site, you'll need to create a username and password--a slight inconvenience, but well worth it to access the treasures inside this site! Once you've logged in, click on "Basic Study Plan" or "Comprehensive Study Plan" to see a menu of the available exercises.
Fragments and run-on sentences are under the heading "Sentence Grammar."

OWL is the Online Writing Lab at Purdue University. The OWL website provides interactive exercises and other information on a range of writing topics.