Getting Started With Spanish by William E. Linney and Antonio L. Orta is a fantastic resource of 177 lessons of mostly grammar that take less than five minutes per day. It’s mastery based, and I believe could be appropriate for children as young as kindergarten. The author provides free pronunciation resources at www.gettingstartedwithspanish.com.

Learn Spanish Vocabulary 101, by Innovative Language is free and comes with a free audio download from innovativelanguage.com

You can typically buy very inexpensive flash cards to develop vocabulary at your local educational store, and I personally am interested in The Complete Book of Starter Spanish and The Complete Book of Spanish for my young children.

Free Spanish Readers For Kindle:

An Elementary Spanish Reader, by Earl Stanley Harrison

Heath’s Modern Language Series:  The Spanish American Reader, by Ernesto Nelson, and Spanish Short Stories

A First Spanish Reader, by Alfred Remy

And most importantly:

The Library!