Please note that these categories describe patterns of behavior, and not necessarily belief systems. You can have all the right beliefs about social equality and still practice oppression through your actions.
This is not intended to be a comprehensive list.
Sexism
Sexism has been an almost universal condition of civilization, probably due to the fact that men tend to be larger and to have more upper body strength than women. This brings with it a greater average capacity for violence, violence is the language of despotism, and we are only slowly moving beyond despotism. Sexism tends to force women into subservient, restrictive roles that many women do not want, and to force men into dominant, competitive roles that many men do not want.
Heterosexism
A subcategory of sexism, heterosexism describes the pattern in which people with clearly-defined genders are assumed to want to have sexual relationships exclusively with members of the opposite gender. Since not everybody does, the outliers can be punished with ridicule, restriction of partnership rights, discrimination, arrest, and even possibly death.
Cisgenderism
Cisgenderism is a social pattern in which people who do not identify with their assigned gender roles, or do not have clearly-assigned gender roles, are forced to either choose gender roles that do not suit them or suffer the social consequences.
Classism
Classism is a social pattern in which wealthy or influential people congregate with each other, and oppress those who are less wealthy or less influential.
Racism
Racism is a social pattern in which people who are identified as members of one specific "racial" group are treated differently from people who are members of another.
Colorism
Colorism is a social pattern in which people are treated differently based on the amount of visible melanin in the skin. It is not the same thing as racism, but the two tend to go together.
Ableism
Ableism is a social pattern in which people who are disabled are treated differently, to an unnecessary degree, than those who are not.
Lookism
Lookism is a social pattern in which people whose faces and/or bodies fit social ideals are treated differently from people whose faces and/or bodies do not.
Sizeism
Sizeism is a social pattern in which people whose bodies fit social ideals are treated differently from people whose bodies do not.
Ageism
Ageism is a social pattern in which people of a certain chronological age are treated differently, to an unnecessary degree, than those who are not.
Nativism
Nativism is a social pattern in which people who are born in a given country are treated differently from those who immigrate to it, to the benefit of natives.
Colonialism
Nativism is a social pattern in which people who are born in a given country are treated differently from those who immigrate to it, usually to the benefit of a specific identifiable group of powerful immigrants.
