First -- Where do you live?
I am the Youth Programs Manager at the Volunteer Center (a division of the United Way in Waukesha County). If you live anywhere near Waukesha County, you could give me a call and I'd be able to give you specific ideas about volunteer opps.
If you do not live near Waukesha, I'd suggest that you start by looking at the actual NEED within your community -- this can be done by contacting your local Volunteer Center, United Way, or by calling 2-1-1 (if your community has this). They will be able to help you make quicker connections to those in need and may have further suggestions on projects that can be done.
Second -- I want to address the comment that suggested that kids could not volunteer with agencies due to child labor laws. This is absolutly false. It is true however, that many non-profit agencies do not accept young volunteers due 1) client confidentiality, 2) liability, 3) unmonitored youth volunteers can be more trouble than helpful. -- With this said, there are still many non-profits who welcome younger children as volunteers as long as they have an adult with them.
Here are a few volunteer ideas for helping kids understand the hardships others face:
*Cooking a holiday meal for a domestic violence/homeless/or other shelter
*Helping sort gifts at the Salvation Army during the holiday season -- kids can help pair gifts for other children to appropriate ages
*Throw a generic "Birthday Party" or holiday party for a children's group -- many non-profits run kids groups so that parents can get the services they need with out the concern of paying a sitter
*Visiting an elderly person -- singing songs for them, playing a game, or just visiting
*Making homemade holiday decorations or tray favors for hospitals, elderly facilities, home-bound meal delivery programs