Volunteer Opportunities for 6 Year Old

I volunteer at a local senior living facility with my kids. I contacted the activity coordinator and review the activity schedule each month, then let her know what days we can come in to help. I don't know where you live and how the facilities are near you, however, this has worked out great for us. We go on average 2 times a month for the past 3.5 years. We have gotten to the know the residents and staff well and the kids love going to help make crafts or play games. The director told me once that she asked the residents what made them happy and they responded with "puppies and kids". BTW my kids are 2 and 4 for age reference.

Bell ringing for the salvation army.
contact a local church and see if they have any ideas

Good for you. I have no suggestions, but this is a great idea.

When my kids were that age, Meals on Wheels was great! Also, we worked with our church to deliver communion to the elderly that couldn't leave there home.

Many official volunteer opportunities have age requirements, so he's probably too young to serve in a soup kitchen or a shelter.
However, there are a few things you can do.
We live near San Francisco, and we often walk through some pretty rough areas as a family (like when we're going to dinner or a play.) I have always taken this opportunity to talk to the kids about how lucky we are, pointing out the dirty, dingy housing, how scary and small the parks are and the number of homeless people on the streets. Not in a "in your face" kind of way, I just point it out and move on. I know they see it and process it.
You might also want to get him involved with Cub Scouts. I was a scout leader for years (both boys and girls) and we did a LOT of community service, everything thing from collecting food for food banks to organizing toy and clothing drives for foster kids to entertaining at nursing homes. It is a wonderful way to teach kids about appreciation for what they have while reaching out and helping others.

I believe "Feed My Starving Children" allows volunteers as young as 5, with a parent. They have "packing stations" in Aurora & Schaumburg.

You might also consider the "Letters to Santa" program through the U.S. Post Office. You could pick out a letter as a family and work together to provide the requested items. Maybe he could do some extra "chores" around the house to earn money to buy a gift.

Unfortunately there aren't a lot of volunteer opportunities for young children due to safety issues/concerns.

Some soup kitchens allow young children to help with setting tables.
He could make cards for the VA hospital.
If it happens to snow, he could help a neighbor shovel.

I hope you can find something appropriate. Good luck.

This isn't so much a volunteer idea, but it worked for us we began to be worried that our son was becoming spoiled and wanted to remind him of how lucky we are compared to so many others. For his 5th and his 6th birthday parties (he is now 6.5) we allowed him to have a big party with all of his classmates, friends and cousins. However, in exchange for this, we asked his party guests to bring a small toy or book in lieu of a gift. The other option was to have a small party with just a handful of his friends. He choose the big party without presents. We then donated all of the toys and books to a hospital. We put this on the invite, and just about everybody brought a donation toy. A few people brought both a donation and a small gift for him, but that was mostly aunts and uncles. For his 5th birthday, we brought the donation to Children's, and this year we did our local hospital in Arlington Heights. It was eye-opening for him to go to the hospitals and see some of the sick kids there. Not only did we talk about how lucky we are because we are all healthy, but also how lucky we are because we are able to have a comfortable life. It really hit home with him.

Another thing we did was watch the documentary "Babies" with him. It followed 4 infants from birth to 12 months - one in Africa, one in Mongolia, one in Tokyo and one in San Francisco. He was fascinated by it and it showed him how other people live so differently than we do. The African baby literally had only a dirty, plastic water bottle to play with, and to this day he still will bring it up when we talk about his toys and how he needs to take good care of them and that he is lucky to have as many toys as he does, etc. He will also mention it to his younger sister when she throws a fit about a toy.