Io Resources
Books

Check it out. And entire book devoted to the place of cows in Ancient Greek culture. Someone is one step ahead of us.
Movies

So the version of Io who guides Perseus in the Hollywood blockbuster, Clash of the Titans, doesn't have a whole lot to do with the Io from Greek mythology, but we sure do like her name.
Historical Documents

Io gets some friendly advice from Prometheus, another victim of Zeus, in James Baldwin's version of the tale.

Our buddy Bulfinch lays out the Greek myths like nobody's business. The story of Io is totally included.
Audio

Don't feel like reading the story of Io? Check out this audio version of the story read by James Baldwin.

Don't worry if your parents don't read you bedtime stories anymore. You can hear Ovid's version of Io's tale from his Metamorphoses right here.