Little soft toys that they can easily carry around--think tiny stuffed toys. "Crinkle Balls' seem to be a kitten favourite. Them main thing to watch for is that the toys have no parts the kittens can pull off and eat! Little balls they can easily roll around are great fun too.
cardboard boxes with holes cut in for climbing and running through. toilet role tubes, pingpong balls, fur mice.
my 9 week old kittens faveroite toy is a bra! go figure...
get a kittenmitten (a glove with mice dangling off on string) or an old oven mitt or two pairs of bedsocks on your hands to wrestle with them. that way they still get to play but leanr human hands is a no-no
Dangly things (even rolled up cardboard or foil) on string to pull along hte floor that they can pounce on. But a word of warning - don't leave them alone with bits of wool or string that they could swallow - lots of cats have had terrible damage from ingesting such things.