For purposes of definition, this web author follows the categorizations of Dr. Walter Martin in "Kingdom of the Cults".  Christian Cults are any religious group that calls itself "Christian", but has a non-biblical view of the person and work of Jesus Christ, or of the biblical way of salvation.  [there are many 'non-Christian' cults also]

For those who just have to have a list, here is an incomplete one (which I'll keep adding to):

There are many fine people in this world who live decent, moral, 'religious' lives, and who follow some system of "Christian" religion that differs from, adds to, or departs from the historical, Biblical "Faith of our Fathers".  They contribute positively to society, and can be very pleasant people to know and be around.  Their lifestyle and personal worth to God is not to be denigrated.  They are creations of God, have 'creative dignity', and produce actual human good.  Their life can be beneficial to themselves and others all of their life - until they face God at the Judgment. 

At the Judgment, their lives are judged "according to their works" (Rev 20:12).  These people may have lived a mostly good life, and their works are good, but what about their sins?  They can never negate their actual sins that they do commit.  Only Christ offers actual "forgiveness", and 'salvation by grace through faith', Eph 2:9  Not of works, lest any man should boast.

People in 'cults' do not actually follow the biblical "Faith of our Fathers", and they do not believe that Jesus' death on the cross is enough - Just ask them. There is always something else required, which is 'good works', and so they teach "another gospel". 

According to the Apostle Paul, these other 'religions' teach "another Gospel" Gal 1:7 "Which is not another; but there be some that trouble you, and would pervert the gospel of Christ."  So, it is not a "Gospel" at all since it is not Good News of salvation by Grace.  It is important to note Paul's use of the specific work "pervert".  Instead of 'grace', all other religions teach some form of salvation by works, so that a person can 'earn' their place in heaven.  That is one explanation of why some members of Christian "cults" can be so 'nice'. They have to be, in order to work their way to heaven. 

Of course, not all "Cults" are benevolent, and not all cult leaders are 'nice'.  The history of the Christian world is full of cult leaders who exploit their followers.  And so, their works show them for who they really are, and real people are hurt, not just in their eternal salvation, but also in this world as well.  In fact, all cults are destructive, because they "pervert" the gospel of Christ, and when people believe "another gospel", they do not have the eternal salvation that is only offered in the Gospel of Christ.   Act 4:12  Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.  

If there was any other way of salvation besides the gospel of Christ, then there would be no need for Christian Missionaries.

Christians are to treat those caught in a cult with courtesy and respect, but cannot have true "Christian" fellowship with the "unfruitful works of {spiritual} darkness".

-  Ike Sweesy

For more information on cults see Cults