From Jeff McCune via the Macenterprise mailing list, he posted a short script showing how to create a user using the command line utility dscl 

#!/bin/bash

## create users in DirectoryService.

DS_ROOT_NODE="/NetInfo"if [ -z "${USERNAME:=$1}" ]; thenUSERNAME="testuser"fi

# We'll leave UniqueUID and GID calculations as an exercise for the reader...

UNIQUE_ID="505"

PRIMARY_GID="80"

REAL_NAME="Test User"

dscl localhost -create "${DS_ROOT_NODE}"/Users/"${USERNAME}" \

 || exit 1dscl localhost -append "${DS_ROOT_NODE}"/Groups/admin GroupMembership "${USERNAME}" \

 || exit 1for PROPERTY in \

    _writers_hint \

   _writers_passwd \ 

   _writers_picture \ 

   _writers_realname \ 

   _writers_tim_passworddo 

dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "${PROPERTY}" "${USERNAME}" \

|| exit 1donedscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" \

"AuthenticationAuthority" ";ShadowHash;" || exit 1dscl localhost \

-append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "AuthenticationHint" "Some Hint..." \

|| exit 1

dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" \

"NFSHomeDirectory" "/Users/${USERNAME}" \

|| exit 1dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" \

"Picture" "/Library/User Pictures/Fun/Fortune Cookie.tif" || exit 1

dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "PrimaryGroupID" "${PRIMARY_GID}" \

 || exit 1dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "RealName" "${REAL_NAME}" \ 

|| exit 1dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "UniqueID" "${UNIQUE_ID}" || exit 1

dscl localhost -append "${DS_ROOT_NODE}"/Users/"${USERNAME}" "UserShell" "/bin/bash" || exit 1

# Create the home directory

mkdir -p "/Users/${USERNAME}"chown ${UNIQUE_ID}:${PRIMARY_GID} "/Users/${USERNAME}"

# From here, you need to set the password