This is one I have used in the past. I printed it, framed it and gave them a diecut of a little bookworm that we had. They loved it!
A Thank You Hiss
Sammy Snake says, "No one's so dear
As a dedicated volunteer.
The ones who come to school each day,
Who work for love and not for pay.
They do so many different tasks,
Most anything our teacher asks.
Like help us write and cut and stuff
And then in math when it gets tough!
They help us do the bulletin board,
A smile from us is their reward.
For they do know, for goodness sake,
It's hard to be a student snake.
We hand them homework every day.
They type and file our things away.
Then sort the mail for everyone
To take back home when day is done.
We're glad they're here, they're really great!
We little snakes appreciate
The ones who spend their time like this.
We hope they like our thank you hissss."
Copyright ©2000 by Bob Tucker
Hope this helps some!