How does the idea of "giving back" work into your religion? Does it at all?
It certainly does. There's a proverb in the Havamal, a poem from the Poetic Edda, that is usually summarized "A gift demands a gift." Thus, the earth gifts us with food, so we should gift it back with offerings; a friend might gift us with help or support, so we should give them a thank-you gift, and help and support them in return. There is also heavy emphasis on the interconnectedness of the local community, which suggests supporting and being a member of that community. Gifts are the things that keep relationships, communities, and individuals within the community strong.
So, charitable gifts would tend to focus on local efforts by and for the community: food shelf, humane society, thrift store, library, school system, etc. (Yes, most library and school systems tend to be impoverished enough to merit charitable giving, IMO.)