Here are some internet games that help students learn about the root words, prefixes and suffixes:

Skillswise Rootwords: You can choose entry, average or difficult level. In addition to the game there is a fact sheet with definitions, a quiz and a worksheet that can be printed out.
Fish Tanks -- This site helps you spell words which have a prefix and a suffix added.
First School Years-- This site has many printouts and quizzes. There are also links to other subjects.
TV411 Vocabulary (1)-- This game allows you to choose a prefix to a word.
TV411 Vocabulary (2)-- This game allows you to choose the correct suffix to a word.
Quia Roots And Prefixes-- This site uses the concentration game to teach the definitions of prefixes and suffixes.
Flamingo game-- Adding the suffix y or ly
Crystal Castle game-- A castle is built as you add the correct prefix to a word.