Hart County Habit for Humanity
(can help with construction, the advisory committee, or donate)
Hart County Humane Society
(can adopt, foster, help raise awareness, or donate money/goods for animals in need)
Hart Life and Pregnancy Care Center
(offers pregnancy/child assistance for needy mothers - and they love help)
The Department of Family and Children's Services could always use foster parents. They also have a great Christmas program to buy presents for the children in foster care to help out the foster parents. They might have other programs if asked - if not, I'm sure they'd be able to suggest somebody who does.
Hart County Clothes Closet is another great option. You can donate any clothes or household items you don't need. If I'm thinking correctly, they still do food drives as well.
There's also an Achiever's Inc. here, but like a lot of Hartwell, they lack a webpage.
There are a ton of miscellaneous opportunities for getting involved in many of the local churches.
Volunteering at the local schools is also a great option. The elementary schools love volunteers to help with reading.
Oh, and there's the Ducks Unlimited local chapter. Believe it or not, they're actually a very highly rated charity in terms of what they actually do with the money they raise.
I had several webpages listed, but the forum made me remove them :/