Amazon offers its Prime members the VTech InnoTab Dinosaur Train Software (pictured), model no. 80-231000, for $5.97 plus $3.99 for 1-day shipping. (Non-members pay $18.29 for this option.) That's the lowest total price we could find by $12. Sales tax is added where applicable. It teaches science, reading, and math skills.

Also available is the VTech InnoTab Cars 2 Software, model no. 80-230100, for $7.49 plus $3.99 for 1-day shipping. (Non-members pay $18.29 for this option.) That's another low, by $6. It features a pop-up dictionary and character creation.

Orders placed today (December 22) by 3 pm ET with 1-day shipping are guaranteed for delivery by Christmas. Don't need it by then? Prime members get free shipping, while non-members can spend $25 or more to qualify for free shipping. (Otherwise, shipping costs $4.12.)