Start a charity registry
One of the easiest ways to do this is to register through WeddingChannel.com. There, you can choose your favorite charity, and every time a guest goes to buy you a gift (like that new KitchenAid mixer or those five-star towels), up to 3 percent of the purchase will go toward the charity of your choice. Another option is to start a charitable registry fund where guests directly contribute money to your favorite charities through a site like Crowdrise.com. (We love Allie and Josh's page if you're looking for a sample.) Also, think about what you're filling your gift registry with and consider a few pieces with altruistic benefits. For example, Macys.com sells pretty baskets woven by women in Rwanda, and the sales benefit the women and their community.
Hire socially and environmentally responsible wedding vendors
The events industry can be a wasteful one -- before you sign on the dotted line with a wedding venue, caterer or even stationery designer, ask them what they do with the leftovers and whether they donate extra supplies. A green vendor doesn't mean “crunchy.” For example, Bella Figura stationery design (with incredible invite suites) donates all its extra supplies to local schools. It also prints on non-tree paper made in wind-powered factories. That's an all-star case, but you see what we're saying.
Use sustainable decor and favors
Tell your florist that you want in-season flowers and plants that don't have to be flown in from out of state. You might even consider arrangements that don't involve cut flowers (and that won't wilt at the end of the night). Potted succulents and orchids make for great take-home favors. Also, avoid wedding favors that create a lot of waste. You could donate to a charity instead of giving out favors, or check out organizations like Cookies for Kids' Cancer. Give everyone cookies as a late-night snack and all the proceeds go to benefit child cancer research.
After it's all over, figure out what can be given away. Some caterers donate to local food shelters and community organizations that could really use the boost. Ask your florist about donating all the arrangements to a local nursing home or hospital. If you're not tied to it, consider donating your wedding dress to an organization like Brides Against Breast Cancer (whose proceeds support programs for cancer patients and their families).
Opt for charitable bridesmaid outings and a volunteer honeymoon
Instead of getting all the girls together to tie bows around ceremony programs or favors, ask your bridesmaids whether they'd like to spend some bonding time together working in a community garden or soup kitchen. Or sign up for a road race or walk and raise money for your favorite cause. Another trend we love: volunteer honeymoons. Instead of a traditional honeymoon, some couples are choosing to visit high-need villages in South America or even Africa to hand out supplies like blankets, books, crayons, clothes and shoes to families and children in need.