Here are some links. Maybe something will strike your fancy:
www.bbyo.org/bbg/ideas/mixers.html
www.meetingwizard.org/meetings/icebreakers.cfm
www.nwlink.com/~donclark/leader/icebreak.html
www.openconcept.ca/index.php/Facilitation/30
Many people love this type of activities, others don't. I happen to be in the set that cringes at the idea. But that's just me - your group may really enjoy them. Personally, if I have to participate, I prefer the less individualized, more anonymous types of activities like when you raise your hand to a series of activities.
"Who Are You?" games are easy if your group is large. You can use a series of questions to learn about them and show similarities/differences. They can raise their hand, stand up, move into the center, etc. for what applies. You can make it serious or funny. In the case of a PTO, questions like?
Have you previously attended a PTO meeting?
Have only 1 child?
More than one child?
Born in XYZ
You can gradually work towards a goal, like asking who has ever:
worked a concession stand
counted money
baked a cake
listened to a child
Gearing up to a finale of establishing they are all "well qualified to be a volunteer".
There are a million ways you can go.
Good luck!