In this day in age I still think business cards have a viable function - especially if you get chatting to someone at a gallery, show, or just about anywhere - as it's easy to pull out a small bit of card with your details already on rather than adding email addresses/ phone numbers into a device there and then. Also, the tangible quality gives the client an incentive to keep it, and will be there to refer back to.
An idea I recently had to distinguish my business cards from generic stock designs, and to give more reason for it to be kept afterwards, is to have my details pre-printed on to good quality stock with the reverse side left blank. Upon meeting a potential client, I'd demonstrate one area of my design services (primarily type & lettering) by drawing/writing a word of their choice for them. This would require me carrying a range of pens around with me, but as I do that anyway I reckon this way of promoting myself will be much more effective than handing out standard cards.
