I think the idea of patron saints is a bit overdone. There are, for example, patron saints of fear of mice and mad dogs. The patron saint of television, Clare of Assisi, lived in the mid-1200s. It seems like patron saints can become a way to market saints rather than strive to imitate their holiness. There are, however, a few patronesses of mothers whose intercession I often ask.
St. Monica, mother of St. Augustine. She raised a saint, so must have done something right! That "something" was constant intercessory prayer for her wayward son. She taught him her faith as a child, then stormed Heaven with her prayers when he turned his back on God as a young adult. I struggle to pray as often as I should for my children, so I keep a holy card of St. Monica up in our kitchen, reminding me of the value of prayer.
St. Margaret of Scotland, mother of eight (including St. David). Here was a woman who knew how to get things done: lead by example. Her holiness, manifest in gentle piety and love for the poor, inspired her husband, the king, and the whole of Scotland. When I am feeling frustrated and short-tempered, I remember the most powerful witness to my children and those around me is to be a living example.
Mary, mother of God. Mary, filled with grace, was called to be mother of our Lord. In uncertainty and sorrow, she persevered in living her vocation. She embodied all virtue and serves as an outstanding example for mothers, but that is not the only reason I look to her. Mary made mistakes. She accidentally left her son in Jerusalem when he was twelve! I take comfort in knowing that the mistakes I make with my children do not mean I have failed or am unfit to be their mother.