Baltimore catechism #1 for the children.
The Sinner's Guide for adults. It's available through iBooks if you have an apple product and may also be in archive.org. Lots of good old Catholic books are on archive.org. Look for ones by St. Francis de Sales, Thomas A Kempis, Lorenzo Scupoli, St Ignatius, St Teresa of Avila,Thomas Aquinas and of course a copy of the Douay-Rheims Bible. All are available in digital format, some through iBooks, some from archive.org
Also do a search for Catholic audio books. There are dozens of great ones sprinkled around the net.