Scoble offers some very interesting advice for business card designs inspired by the thousands of business cards that he collected during his career.

He shares a very interesting business card design:
Matt Mullenweg’s visiting card says simply "1. Go to google.com. 2. Type in "Matt." 3. Press "I’m feeling lucky." (It also has his phone number on it).
Agree with all the points mentioned by Scoble. Just adding some more business card tips below:

You must always carry business cards in your wallet - you can encounter interesting people anywhere anytime.

Also, before sending the business cards for printing, check for typos atleast three times. Make sure the font is right so that 0s in the phone number don't look like 8 or even vice versa.

Business Card designers are really bad at typing email address and web domain. They will either forget the dot in your URL or change the location. If that happens, people will not be able to find you or reach you via email.

Don't waste the backside of the business card. Use it to write about yourself or your company or even put a map of your business. I know some people who add conversion tables at the back of their visiting cards.

Don't opt for plastic business cards. They don't look professional.

While exchanging business cards, handle the other person's card very carefully - don't bend it or slide it in your trouser pocket. Instead, neatly place it in your wallet or briefcase. Show respect.