For those with babies or younger kids, I bought this and it helps tons with sun that would otherwise be shining directly in my daughter's face through the rear window.
[ame="http://www.amazon.com/gp/aw/d/B008VM0TLO/ref=ya_aw_oh_pit"]Shade Styx ERT-RW39 Black Universal Rear Window Sunshade Kit:Amazon:Automotive[/ame]
Pics aren't that great but you get the idea.