Toss the Frog
This is a great activity for a hot summer day. When kids are tired of the game, they can splash into the pool. Fill up several kiddie pools with water, or if you have a large swimming pool, use that. Cut lily pads from flat pieces of green Styrofoam. Give kids lightweight plastic frogs and tell kids to throw the frogs onto the pads. If they are able to land a frog on a lily pad, they get a point. Let kids keep their frogs as souvenirs.
Catch Flies
This game is great for younger kids and will assist them with oral development and motor skills. Take several party favors, the kind that unroll a strip of colored paper when you blow into them, and glue a small square of Velcro on the end. Buy lightweight plastic bugs and flies and stick Velcro squares on them. Give the party favors to the kids. Tell the kids that they have to pretend to be frogs, blow on the favors, and try to catch a bug.
Leap Frog
This is a classic game involving frogs and is perfect for any frog-themed party. Have kids form a line and crouch down in the "frog" position. Make sure there is at least the space of one child between them. Have a child start at the back of the line, jumping over each child while lightly tapping the back of the child he's jumping over. It's best to play this game on carpet or grass and ask kids to remove their shoes. Consider playing music while the kids jump.
Frog Hunt
Even if you live in an area where there aren't a great deal of frogs, you can still provide kids with the benefit of a frog hunt. Hide plastic or rubber frogs around your house or yard. Make sure that you tell kids clearly the parameters of the area where you've hidden the frogs, so that they're not wandering to areas of the house that are off-limits. Let the kids keep the frogs they find.