I've always loved letterpress. There's something about the feel of indentations in the paper on thick, beautiful card stock that makes me so happy. I have such an appreciation for the art form and traditional press process and it just adds so much more to the design than a traditional digital print. Here are some samples of my favourite cards that I've been given, along with a few other great pieces of work I have found.
Here's one more link to some stunning letterpress packaging: http://www.thedieline.com/blog/2014/10/13/slik-letterpress-box.
Though expensive, this type of printing really makes a design stand out so I encourage you to make the investment on your next project!