There's not as much as a variety with spongeballs. The only true effects you can do is basic producing, disappearing, and teleporting them. If someone will correct me if I'm wrong, there fun and all but need more variety.
As others have said, they can change color (in someone's hand if you like) and change size (i prefer going from a 2 inch to several 1 inch balls) or change shape (square sponge ball anyone)? I do a Halloween routine where the black and orange sponges change color, multiply and then transform into a giant jack-o-lantern sponge.
in SPONGE by Jay Noblezada you can learn a entire routine of spongeballs. Not an act, but a 10- or 15-minute-long routine.
Don't get Sponge - the technique taught isn't the best. The better resource is Spongeball Toolkit (where you will learn the best way to wash spongeballs). It also will give you a bunch of great ideas and provides some great props to use with your routines. Also, the routine in Mark Wilson's book (if you ignore his advice to point to the hand where the ball is supposed to be) is great.
There are some great effects you can get like sponge bunnies, sponge ball Blendo, Sankey's Earplugs and my favorite, Pips a Popping. You also can get lots of different shaped sponges, some of the best are by Alan Wong - bananas, eggs and sushi.
