There are other ways to support your son as he develops as a reader. As you know, there are many words that are found time and again in written language. These words are referred to as high-frequency words. As your child gets older, he will need to learn to immediately recognize more and more high frequency words. You can purchase pre-made flashcards of these words, or make your own, and work with him on a daily basis to memorize these words.
Software is another useful teaching tool.
Many programs also allow parents to assess their child's progress, too, which is helpful in setting the levels and gauging the effectiveness of a given program. Although there are a lot of fun ways to teach and reinforce reading skills, there is no replacement for the thirty minutes per day of reading practice. Make weekly trips to the public library to replenish your supply of books. Allow your child to select his own books, but be sure to monitor his selections by using the five-word test. Many libraries also have reading lists for each grade level, which may help you to guide your son's selections.