Right Now at VTech, buy two software cartridges for Mobigo, Innotab or V.Reader and get one free. Use code swget1_2 at checkout through 12/9.
That comes out to about $16.66 each for Innotab and $13.33 each for Mobigo. Free shipping on orders over $49.
Keep in mind that other stores might be running sales, too, so do a quick price comp with any shipping costs included before you buy to ensure that you’re getting the deal you think you are. Walmart, for example, has several Innotab titles as low as $16.34.