Cool eco wedding favors - personalized sigg bottles!, originally uploaded by bella figura letterpress.
I am not sure how much these cost, but personalized aluminum waterbottles are definitely a way to help the environment AND give your guests a thank you gift they can use.
Here's the photo note for more info:
For a Bella Figura blog post on eco wedding favors (http://www.bellafigura.com/letterpress-inspiration/). Photo from Sarah Pants's Flickr - www.flickr.com/photos/sarahpants/2958558742/in/set-721576...
This was a wedding that Bella Figura printed some fabulous letterpress wedding invitations for.