Some friends with a 4-month old kid recommended we get this silly-looking Lamaze Multi-Sensory Clutch Cube; their kid totally loved it, they said, it's by far his favorite toy.
Well, we got one, and our kid loves it. At first, all she could do was spaz out, and she'd accidentally hit it away. We counted this as great success, until we strung it up a few inches over her chest. Then she could spaz out and hit it over and over. Now, she grabs it, chews it, swings it, and studies it intently. In fact, we often leave her alone with this magical cube, which keeps her entertained while we head to dinner and a movie. (JUST KIDDING.)
All this magic can be yours for $12.99 at Babies R Us
My 7 mos. old son has had this cube since he was born and he still loves it. And as he develops dexterity, it remains useful with the different handles and whatnot. There's a lot too it - it's definitely worth the price.
Per your suggestion we got this cube. The first time I showed it to my 3 mo old girl she smiled! It is still her favorite toy, good to look at and good to chew.