These are some great educational materials, and Amazon has a pretty good sale right now. Maybe they'd make great summer tutoring materials to get your young ones ready for kindergarten or keep their skills sharp for next year. Letter Factory is probably the best video there is for teaching the beginnings of phonics skills to young ones.
What I see for good prices, Letter Factory alone is under $10, but they have some great bundles under $20 for a few DVDs, flash cards, and CDs. Here's the link to all the ones that are on sale.