Consider doing an outdoor event or a venue with lots of windows so that you can try to conserve energy. Research venues that are certified with LEED (Leadership in Energy and Environmental Design); they use their resources more efficiently.
Look for caters who use organic or sustainable products, including dessert and even wines! Check out Whole Foods or Trader Joe's.
There are many eco-friendly invitations and paper products you can find. Get creative and find other ways to say what you want on paper, doubling your menu and table numbers together, or printing your RSVP's on a postcard.
Decor and Gifts
Think of some new ways to incorporate environmentally friendly decorations into your event, from organic flowers or potted plants as your centerpieces to soy candles, organic sweets, and seeds for planting later as party favors.
Photographers that use digital photos are being green by offering you an internet gallery instead of printing proofs on so much paper. Companies like Bryant Sentosa's Photoboothless offers the option of putting your photos up on a website to download instead of printing copies at the party.
So go out there and save the world, one event at a time!