It makes me sick to think that we might not have at least one of our invitations from our wedding for a keepsake....I have to check on that.
We made our own (which is a great way to instill this part of the wedding experience with meaning (and a lot of work)).
In the meantime, Think about using alternative materials for the invitations. As I have mentioned before, DH is a furniture designer. We incorporated walnut veneer on our invitations. Other materials/ideas we used were vellum, a shimmery slate blue, and an orchid design.
Our friends tied their own invitations together with ribbon. I've seen invitations printed on biodegradable paper that has seeds in it. I've seen Tarot Cards used as the backing of some invitations...
One thing that would be cool is an invitation inspired by a cake I saw on that show, Ace of Cakes, on FoodTV. I sketched it.
I don't know exactly how it was made, but it looked like a tiered cake was either frosted or covered in a thin veil of light-aqua fondant. Then, it looks like someone rolled out a slightly thicker veil of chocolate brown fondant, die-cut deep-ish flower sillouhettes in the fondant, and then laid it on top of the aqua. The aqua flowers popped from behind the brown. It looked almost like velvet burnout fabric or something. I think it would be cool to do the same thing with differently weighted papers.