The right business card can leave a good impression, however after a while they can all start to look the same. You could always make a PCB card with a working circuit, or for something different create your own hand-held business card printer in the same manner as Instructables user Thingking has done.
By using a small Arduino-compatible board with an inexpensive thermal printer (and a hidden battery pack!) you can quickly print out a card of your own design. Although it won't last long being on thermal paper, it gives you a point of difference and would be a fun way to share your details with others at hackerspaces and other social events.
Apart from being one of the smallest Arduino-compatibles on the market with USB, it also has an onboard RGB LED and piezo which can be used a knock sensor and various tune and sound effects. Plus you can add extra circuitry with the matching protostick! For more information and to order, click here.