St Gertrude the Great?
Okay, so who the heck is St. Gertrude, and what makes her so great? Heck, she's the only female saint called the Great. Why?
St. Gertrude was an orphan, her family name unknown, who was raised by Benedictine nuns and brought into their community. Like most nuns at that point in medieval times, she was a scholar. Initially, she was more interested in her studies than her God, but when she was 25, she had a change of heart. From then on she became a great mystic and had the requisite visions, miracles, and so forth... but she also wrote Latin works which were helpful in spiritual life. St. Teresa de Avila, for example, chose her as her model and guide. TAN is apparently publishing some of these works under the title of The Life and Revelations of St. Gertrude the Great. She also wrote a set of Spiritual Exercises which are still used today in some communities.
Here's a short but very useful intro which also tells you why she's "the Great".
As always, we can consult the Catholic Encyclopedia.
Another good page on St. Gertrude. This one is part of a POD, do-it-yourself lay apostolate: The Mission to Empty Purgatory. Yes, they mean to empty purgatory by using St. Gertrude the Great's prayer, which allegedly releases 1000 souls per time said. Yes, they have a pledge page. Yes, they have a page to show how close they've gotten to their estimated goal: only 90 million some to go.
Dang, we American Catholics do think big, don't we? Hee! Let's do it!
(Somewhere, my poor Evangelical friend Joy is cringing and wondering what Maureen is going to advocate next....)
Also , one of our "traditional" separated brethren has created a whole webpage on just this saint! It's good info, so ignore the radtrad nonsense and use the good stuff, in the real Catholic tradition of despoiling the Egyptians. :)
Here's some information on her devotion to the Sacred Heart.