This question refers to people who believe that Jesus is a Created Being. Who are these people? Which groups who identify as Christian teach that Jesus was created? I'm guessing they're not professors of the Nicene Creed "Begotten not made". Is there one name to refer to such a classification of Christians or are they a multitude of denominations?
There are several denominations who believe that Jesus is a created being. Jehovah’s Witnesses are probably the most vocal in their belief that Jesus, in his pre-mortal existence, was created by Jehovah God as the mighty spirit creature known in heaven as Michael the archangel. It was the spirit of Michael who entered into the child born to Mary and who became known as Jesus. 
Another group who believe that Jesus is a created being are Latter Day Saints (Mormons). However, they differ from every other group because they also say the God Elohim, the literal parent of a spirit son called Jehovah (who then had to come to earth to be born as Jesus), was originally a man. 
Way out on a limb is the Unification Church (Moonies) who say Jesus is a finite separate being, the offspring of Zechariah and Mary. Since this group is considered to be a cult I do not propose to say any more about them, other than to refer to the book below. 
Source  chapter 8;  chapter 10;  chapter 17: ‘World Religions and Cults – Counterfeits of Christianity – Volume 1’ edited by Bodie Hodge & Roger Patterson, published 2015.
The clue as to what ‘umbrella’ best covers groups that say Jesus is a created being is ‘Unitarianism’:
Whereas Trinitarianism teaches that God is three in one (triune), Unitarianism teaches that God is simply one (unity). Unitarianism rejects the doctrines of the Trinity and the deity of Christ. Unitarianism should also be distinguished from Modalism, which is also non-Trinitarian. Modalism teaches that Father, Son, and Holy Spirit are three modes of existence for the One God. Modalism is found today in the United Pentecostal Church. While both Modalism and Unitarianism are non-Trinitarian, Modalists affirm the deity of Christ. Unitarians teach that Jesus was an inspired man, a great teacher, and an example to follow but certainly not God.
Unitarianism began to flourish in various parts of Europe. Gradually, a number of individual ministers in the Church of England embraced Unitarianism, and, later, Unitarian societies were formed. These beliefs also spread to many Congregational churches in New England in the 18th century. Harvard College, which had been founded for the training of Calvinist ministers, swung to Unitarianism with the election of a Unitarian minister to the Hollis Chair of Divinity in 1805. https://www.gotquestions.org/unitarianism.html
Unitarianism rejects the deity of Christ and claim he is finite, with a beginning. They believe that God is One Being and that Jesus is not the eternal Son of God. Probably the best known is the Unitarian Universalist Church.
Unitarian thought and Universal thought were merged together during the late eighteenth-century in America during the Age of Reason... To the Unitarian Universalist, Jesus was a good moral teacher, but nothing more. He is not considered to be divine, and every miracle associated with Him is rejected as being outside of human reason. https://www.gotquestions.org/unitarian-universalism.html
Then there is Biblical Unitarianism:
Biblical Unitarians deny the Trinity, teaching that God is one being (hence the word Unitarian in their name). Jesus, according to Biblical Unitarianism, is not the eternal Son of God; rather, He was created by God in the womb of Mary. Jesus was later exalted by God and given authority over creation, making Him like God, but He remains a finite, separate being with a beginning. ... Organizations that fall under the category of Biblical Unitarianism include the Church of God General Conference (CoGGC) and the Christadelphians. https://www.gotquestions.org/Biblical-Unitarianism.html
Regarding the deity of Christ, Christadelphianism teaches that Jesus was more than a man, but less than God. According to A. Hayward, in Great News for the World, p. 41, Jesus was a created being with “strength of character to right some of the most appalling wrongs of his time.” Christadelphians teach that Jesus had a sinful nature and he, too, needed salvation from sin, that he was not pre-existent and did not come into existence until he was born in Bethlehem. https://www.gotquestions.org/Christadelphianism.html
I’m still searching for other groups that say Jesus is a created being, but I think that’s enough for now!
EDIT: I’m not sure if the Cooneyites, or Two by Two’s, believe Jesus was created prior to coming to earth, but from the research I conducted on this group, they appear to deny the divinity of Jesus:
The Two by Twos are anti-Trinitarian. The Holy Spirit is perceived as an attitude or force from God. Jesus is a fully human figure who came to earth to establish a way of ministry and salvation, but He is not God Himself. The Two by Twos believe that Jesus overcame His own flesh. Great stress is laid upon following the example of Jesus but less emphasis on Jesus as Savior—Jesus’ life is more important than His death. https://www.gotquestions.org/Two-by-Twos-Cooneyites.html
It is also noteworthy that Muslims deny that Jesus pre-existed before he was born. However, I took the original intent of this question to refer to Christian denominations.