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Fun education for Preschool level
By an Amazon.com customer
Big Words for Little PeopleBig Words for Little People by Jamie Lee Curtis
Buy new: $11.55 / Used from: $5.42
Teach your child not to be afraid of new words. Excellent resource for fun learning, sight recognition and word association.
What Your Preschooler Needs to Know: Get Ready for Kindergarten (Core Knowledge)What Your Preschooler Needs to Know: Get Ready for Kindergarten (Core Knowledge) by Core Knowledge Foundation
Buy new: $12.24 / Used from: $10.86
Excellent resource. Goes with 2 activity books also listed.
What Your Preschooler Needs to Know: Activity Book 1 for Ages 3-4What Your Preschooler Needs to Know: Activity Book 1 for Ages 3-4 by Linda Bevilacqua
Buy used from: $72.11
Core education for 3-4. Some may be repetitive to things already taught, but activities are set up to make it easy to expound on the ideas and make new activities with this as a basis.
What Your Preschooler Needs to Know: Activity Book 2 for Ages 4-5What Your Preschooler Needs to Know: Activity Book 2 for Ages 4-5 by Linda Bevilacqua
Buy used from: $72.11
Second resource book for the "Get Ready for Kindergarten" book. Slightly more difficult activities, very suitable for this age range.
Spectrum Letters and Sounds (Little Critter Workbooks)Spectrum Letters and Sounds (Little Critter Workbooks) by Mercer Mayer
Buy new: $9.95 / Used from: $1.95
Good basic worksheets. Not a lot of guidance here, but a good, colorful way to offer worksheets to your child.
LeapFrog®  Tag Reading System (16 MB)LeapFrog® Tag Reading System (16 MB)
Buy new: $46.99
Wonderful for independent exploration and to encourage early readers. Books and flash cards can be purchased for this reading wand. The only bad thing is that you can only hold about 5 books/items in memory once they've been downloaded.