The Wordly Wise 3000 program is great. My daughter actually enjoys vocabulary now. Just be careful, this is not a Christian program and there have been stories that go against my faith. But, I do the comprehension stories with my daughter and use anything we don't agree with as a teaching moment. In a way it's good, my daughter knows she can't believe everything she reads and is learning to be a critical thinker. So, despite the secular world-view. I still recommend this product ... just be cautious if you're Christian, your children do all the work independently and don't have great critical thinking skills.
I began using Wordly Wise with my third child when he was in 6th grade. He found he really liked the program overall and felt like he was learning vocabulary better than with my former method. This year, I bought Wordly Wise books 5 and 6 for my 5th grader and books 7 and 8 for my 7th grader. Since there are only 20 main lessons, a child can complete one book and begin the next in the same school year. I plan to have them pick up this fall wherever they left off this school year, and continue onward. My goal is for them to complete 3 grade levels of vocabulary over 2 school years.
Although there is evolutionary material in these books, I feel that this is a good program if your kids are able to ignore it, or if you are willing to deal with the topic when it comes up.
I grew up using Wordly Wise and now use these with all of my homeschooling kids. These books are amazing and not only help expand your child's vocabulary, but also help them understand use of words in context and their meanings. We use these daily and my kids vocabulary has expanded so much as a result.