Dime a dozen - what does a dozen dimes equal ($1.20)
On cloud 9 - someone is on 1 of 9 clouds = 1/9
It takes 2 to tango - write the fraction of people (maybe 1 girl, 1 boy)
One jump ahead of (a frog). - write the fraction of the other animals in line.
Take five - write the fraction, five of what
Dressed to the 9's - how many 9's on a dress
Catch 40 winks - make an array
Feel like a million bucks - explore three addends, what would equal 1 million
Art and writing idiom activities - Minds in Bloom and Idioms by Kids.
3rd Grade Grapevine has a free printable for kids to draw and write their idiom's meaning.
List of Idioms - Number, Money, Animal, Color, Food, Various