Mine gets handed to any potential sub or vendor so I go through quite a few. I also have cards available at trade fairs or recruiting events. It does gets little annoying when I get calls b/c someone gave out my card, but a necessary part of the job.
www.vistaprint.com sell business cards at a great price. I particularly like the magnetic cards. These type of cards don't ususally get filed, they are stuck on refrigerators or metal walls and remain in plain site. I switch back and forth between paper and magnetic or give out one of each to some contacts.
Cost for good glossy finish on good paper $.12 each
I've had Business cards on several jobs. Usually, I have them made myself. Many Company cards have tiny print and large logo's and are hard to read. When I was in Sales I'd leave 2 or 3 on lunch counters, Dry Cleaners & everywhere I spent money.
When I was in the Bail Bond & Beeper Business I'd throw 2 on the sidewalk of Drug Dealer hangouts and Hot Spots.
Day Job - I send out my biz card all the time to customers, lots of useful contact info for different departments they may need in addition to my contact info.
Personal business cards - all the time. I'm in sales and have come across a lot of career opportunities just by striking up a conversation with someone over a beer at the local pub. I've had people call me 6 months, a year later when they come across my card and have an opportunity they think might interest me.
I will also give out my business card to some girls I meet as an easy "look me up, etc". I do that less than for business opportunities obviously, but I've gone on dates with girls months after we originally met because they come across my card cleaning out their purse, etc. The key is remembering who you gave them out to as you don't want to look totally clueless if you get a call from a slim out of the blue and you are like "which one were you again, I meet so many girls at that bar named Brandi "