On Mac OSX, the native SSH client can use the built-in keychain directly. To add your private key to the keychain simply use the command:
ssh-add -K /path/of/private/key
As an example if your private key is stored at
~/.ssh and is named
id_rsa, you would use the command:
ssh-add -K ~/.ssh/id_rsa
You will then be prompted for your passcode, which will be stored in your keychain. After this you should be ready for a password-less login.