Not a of information is required for this kind of thing, so I finally had a use for the little skeleton hands I picked up some time ago. (I've seen them in dollar stores since, although I bought them elsewhere.) I'm not trying to be cheap - I've actually been collecting things with this kind of thing in mind and am thrilled that I finally get to use some of them.
I used a mini template of my own design (I like the kind that open on the short end) to make the small business card-size envelopes out of my "signature" (until it runs out) chartreuse paper. I used some gray ink to make the paper look a little distressed.
I just printed out my info. on ivory cardstock, using a business card template and trimmed the cards to fit the envelopes and rounded the corners using a little tool available in the scrapbooking section of craft stores.
Finally, I used some 2-sided mounting foam to attach the envelope to the hands. I slipped each little missive into a treat envelope and sealed it with a round label. Each of those went into a padded envelope with custom address labels (more chartreuse paper).
For several reasons, we have to keep the guest list for parties pretty small. One tiny benefit is that it's not cost-prohibitive to spend a little extra on postage, etc. since we aren't sending out that many.