Add this to your .bash_aliases for fun and profit:

function Snapshot () {
  local dst=""
  local atnam=""
  if [ -z "$1" ]; then
    dst=`df -l . | tail -1 |awk '{print $1}'`
  else
    if [[ $1 = *@* ]]; then
      atnam="${1##*@}"
      dst="${1%%@*}"
    fi
    dst=`df -l "$dst" | tail -1 |awk '{print $1}'`
  fi
  [ -z "$dst" ] && echo "wants file system name to snapshot" && return 1
  local NOW=`date +%Y%m%d-%H%M%S`
  [[ $dst = /* ]] && dst="${dst#/}"
  [[ $dst = */ ]] && dst="${dst%/}"
  [[ x$atnam = x ]] && atnam=$NOW
  sudo zfs snapshot "${dst}@${atnam}"
}