From my Linux time, I know that ssh-copy-id is extremely handy. Sadly its not available on OS X.

But nonetheless, thats how you can setup a password less login to another host from OS X:

# Generate your local public/private key (if not already done)
# (you can press enter to accept the defaults)
ssh-keygen
# Create the remote directory (especially for Windows hosts)
ssh user@host.com mkdir "~/.ssh/"
# Copy the public key to your remote host
scp .ssh/id_rsa.pub user@host.com:"~/.ssh/"
# Add it to the authorized_keys File
ssh user@host.com "cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys"

And your done!