Find a beach or river where you can collect small flat stones.
Be sure to have permission to take stones if it's on private property, and only take stones from places where you're permitted to.
Step 2: Prep the stones
Clean 'em with soap water, then dry them. It's not that complicated.
Step 3: Make it a business rock!
Use a fine tipped sharpie and write out all the information you'd normally give out on a business card. I usually put my name, phone number and email address.
Step 4: Thoughts
This is a fun and creative way to hand out contact information. People aren't going to forget this very easily if you give them one.
One downside is that they don't fit in wallets. An upside, on the other hand, is that no one else has business cards like these!