Today is the feast day of St. Thomas Aquinas, the date being changed from the traditional observance on the date of his death to his birthday after Vatican II.
There are numerous quotes and links to images and writings here. The Stanford Encyclopedia of Philosophy has an extensive article here. The Catholic Encyclopedia article is here, and their hyper-linked edition of the Summa Theologica is here. Christian Classics Ethereal Library has links to works by and about him here. The Internet Encyclopedia of Philosophy has information on his life and writings.
The SOAJ has a prayer:
Almighty God, who hast enriched thy Church with the singular Learning and holiness of thy servant Thomas Aquinas: Enlighten us more and more, we pray thee, by the disciplined thinking and teaching of Christian scholars, and deepen our devotion by the example of saintly lives; through Jesus Christ our Lord, who liveth and reigneth with thee and the Holy Spirit, one God, for ever and ever.
The picture at the top of the post is of Fra Angelico's painting.