I recently made some Halloween party invitations. The only cost I had were for the stamps and card-stock. I found the invitations from here and printed them on black card-stock which I found at Michael's on sale. I then added a yellow ribbon to the invites for an extra touch. I made the envelopes black using spray paint and sealed them with a clear gloss coat. I originally had the skeletons printed out for the invites but ended up liking the orange ones better, so I tucked the skeletons into the envelopes for an extra surprise!
The invites printed on black card-stock
The skeletons bunched up to insert into the envelopes
I paper holed punched and tied their "joints" together with yarn
I sprayed painted the envelopes semi black
I sealed the envelopes with a clear gloss coat of spray paint to keep the black from rubbing off
My address labels I printed