Tossing a favorite teething toy onto the floor is a great game -- for your baby, if not for you. When she's around 8 months old, she'll also start looking to see where it landed (though you'll still be the one picking it up).
When your baby stays interested in things after they've left her line of sight, it means she's developed object permanence: She now realizes that people and things exist even when she can't see them. The downside to this development is that she'll probably cry when you leave, but it also opens up a new set of games you can play together. Until she's mobile enough for hide-and-seek, she may love:
Tuck a stuffed animal under a blanket, then pull it back so you can both greet Teddy again. Your baby will catch on and do it herself. (Warning: The older she gets, the more times in a row she'll want to play this!)
Don't just hide your eyes: Duck behind a doorway or the couch for a second before you pop out.
While you're making dinner, give her a set of measuring spoons to play with for a few minutes, then hide them in a plastic container with a lid she can pull off. (That'll buy you more time to peel vegetables!)
Before long, your baby will know to look in the same place for certain things, like toys and books. Which is not to say that she'll put them back where they belong....