Parklife Press- a wonderful example of letterpress invitations. This little North Carolina company is based in North Carolina, but will work with you wherever you are! They are flexible, personal, can work quickly and are very affordable. They also use tree- free, acid- free cotton paper.
This is the latest design for Parklife- Quill. It is beautiful!
Other favorites of mine are Arboretum and Velvet Waltz.
There are several designs perfect for a "green" wedding. Orchard and Californian are examples of these. So, go to Parklife's site and look at all of the simple and elegant designs. They are unique and beautiful!