Each Sunday and Holy Day the Order sends out prayers and readings to the mail list and posts them on this forum. This is the traditional Western lectionary. You might wonder how these prayers and readings were selected. Well, the prayers come from the 6th Century (or before) and were recorded by three bishops of Rome concluding with Gregory the Great. The prayers and appointed readings were published in English in 1549. Consider this on the readings.
There is one more important way in which Scripture is authoritative for the people of God in worship and this is rarely spoken of, or explained these days. ... the Eucharistic Lectionary, those portions of holy Scripture appointed for the Epistle and Gospel through the Christian Year. These are not random choices of biblical passages but were put together around the fifth century or earlier to communicate essential doctrines of the Christian Faith concerning our Lord Jesus Christ and salvation and sanctification in his Name. There is a natural division at Trinity Sunday. From Advent to Trinity Sunday there is a great emphasis on Dominical Holydays, and thus of the manifestation of the Lord Jesus in space and time, who he is and what he is, which are the foundation of Faith. After Trinity Sunday we enter the non-festal part of the Christian year where the emphasis is on what Jesus and his apostles teach us about the Christian life.
[Peter Toon, Doctrine as Doxology, 2006]
Another source with lots of extras, like homilies, is http://www.lectionarycentral.com/
IN HOC SIGNO VINCES - TIME DEUM ET OPERARE IUSTITIAM