My Wom-po poetry listserv suggests the following collections for young children.  I’ve pasted in recommendations from eight different women.
                                                     
Regarding poetry kids still love (and grownups too)-- has anybody
mentioned Milne?  He might tilt toward the younger side of the age-group
in question, but who, I ask you, can resist the fun of I AM SIR BRIAN
KERSPLASH?  And the trimeter nuttiness of JAMES JAMES MORRISON MORRISON
WEATHERBY GEORGE DUPREE??

One of my favorite poetry books as a child was a light-verse book by John Ciardi called The Monster Den, perfectly illustrated by the late great Edward Gorey. I think they teamed up on a couple of other such books too, but I liked that one best. And of course Shel Silverstein.



Brats by X. J. Kennedy and Opposites by Richard Wilbur are great fun.

 

Check out Naomi Shihab Nye's anthologies This Same Sky (poems from around the world that children can enjoy, but not specifically written for young readers), The Space Between Our Footsteps (poems and paintings from the Middle East, Salting the Ocean (poems written by children), This Tree is Older than You Are (poems and paintings from Mexico).

 

Two of Naomi Shihab Nye's anthologies are especially useful: This Same Sky (acollection of poems from around the world) and Salting the Ocean (100 poems by children).  (This is another woman’s endorsement of the same books.)
 
And check out the Children's Book Council.
Start here for a list of poetry books:
 
http://www.cbcbooks.org/html/showcase_mar-apr_2003.html
 
Then click on "Children's Poetry Week" for other resources.

 

Randall Jarrell's "The Bat" is always a big hit. I've used it first grade through
middle school.

I'm very fond of Theodore Roethke's collectin of children's poems "I Am, Said the Lamb."

 

Are you familiar with Kenneth Koch's two anthologies of poems by and for
children? _Wishes,Lies,& Dreams_ and _Rose, How Did You Get That Red?_

 

"Questions My Son Asked Me, Answers I Never Gave Him" by Nancy Willard (
in _Household Tales of Moon and Water_) is a fun poem for parents,
teachers, and children to share together.
 
A good anthology is _Learning by Heart: Contemporary American Poetry
About School_ by Maggie Anderson and David Hassler. Many of the poems
wouldn't do for second graders, but "School Buses" by Frank Kooistra is
a lovely, tiny poem in it that would, as would several others.