We sometimes by a case of Clay/Skeet from WalMart. You get about 90 of them for 4 bucks. At 30+ yards with a pistol is kind of fun. You can make up little competitions with them and its cheap!
Charcoal briquettes works too, its just smaller.
I have also seen an older fellow teaching his grandkids to shoot a .22 using animal crackers at 25 yards.