Business cards and postcards
They need not be corporate-style business cards form some trashy 80's movie. As with anything else you give to someone, they should ideally reflect your practice - perhaps with an image on one side, or be hand-made or reflective of some other aspect of your practice. Home printers let you print your cards at home and still include images. Lettering sets or printed labels enable you to add short-term information such as an upcoming show on the back of a standard business card.
Postcards offer much the same possibilities but with a larger, better resolution image on one side. Additionally, these could be sold as well as given away, if you can find someone to stock them and sell them on your behalf, and you can afford to have them printed in good enough quality in the first place.
See the listings of printers for affordable options.