We just bought a new portable DVD player for our son that can read SD memory cards, can i put some movies on that kind of card?

Buy/download movies online (legally preferably) or rip your DVDs to your computer.

Use a file converting program (google it) and put them into a format that the DVD player can read. (see the box for supported video formats)

Drag and Drop onto SD card.

You’re done.

Make sure you get an SD card that is big enough. If you get one that is only 256 MB or something small like that won’t have enough memory to fit an entire movie. I would get a 2 GB, 4 GB, or even an 8 GB card so that you’ll have enough memory to hold one or more whole, high quality movies.