I sometimes use them as a marketing piece. Art (or until recently for me, pieces from my corporate portfolio) on the front, info including contact info on the back. Depends on my mood, intention, etc. Sort of like a sample or mini resume, calling card, etc. I want people to contact me for more!!
Sorry it's so mercenary of me, but it helps to pay my supplies habit... (and chocolate)
In 1996, I made a "resume" into a booklet of several pages of black ink printed onto brown paper bags, tore the edges, mounted on black linen cardstock and bound them. I got a terrific response, but when people called or wrote me to tell me how much they liked them, they said that sadly, they had no work for me. One gal said she displayed it on her desk, LOL! In 2001, I got a call from someone who had kept it and referred me to a freelance job.