The Revised Common Lectionary is a three-year cycle of weekly scripture readings. The RCL is built around the seasons of the Church Year (begins with Advent), and includes four readings for each Sunday. During most of the year, the readings are: a reading from the Old Testament, a Psalm, a reading from the Epistles, and a Gospel reading. You can find the readings for each week here.
We are currently in Year C of the three-year cycle: