How can I measure my unconscious prejudices regarding religion, race, gender, age, obesity, etc?

Answer: Take the Implicit Attitude Tests (IATs) at Project Implicit.

From the Project Implicit website:

Select a Test

Gender – Science. This IAT often reveals a relative link between liberal arts and females and between science and males.
Weapons (‘Weapons – Harmless Objects’ IAT). This IAT requires the ability to recognize White and Black faces, and images of weapons or harmless objects.
Gender – Career. This IAT often reveals a relative link between family and females and between career and males.
Sexuality (‘Gay – Straight’ IAT). This IAT requires the ability to distinguish words and symbols representing gay and straight people. It often reveals an automatic preference for straight relative to gay people.
Skin-tone (‘Light Skin – Dark Skin’ IAT). This IAT requires the ability to recognize light and dark-skinned faces. It often reveals an automatic preference for light-skin relative to dark-skin.
Presidents (‘Presidential Popularity’ IAT). This IAT requires the ability to recognize photos of Barack Obama and one or more previous presidents.
Age (‘Young – Old’ IAT). This IAT requires the ability to distinguish old from young faces. This test often indicates that Americans have automatic preference for young over old.
Religion (‘Religions’ IAT). This IAT requires some familiarity with religious terms from various world religions.
Arab-Muslim (‘Arab Muslim – Other People’ IAT). This IAT requires the ability to distinguish names that are likely to belong to Arab-Muslims versus people of other nationalities or religions.
Race (‘Black – White’ IAT). This IAT requires the ability to distinguish faces of European and African origin. It indicates that most Americans have an automatic preference for white over black.
Weight (‘Fat – Thin’ IAT). This IAT requires the ability to distinguish faces of people who are obese and people who are thin. It often reveals an automatic preference for thin people relative to fat people.
Disability (‘Disabled – Abled’ IAT). This IAT requires the ability to recognize symbols representing abled and disabled individuals.
Asian American (‘Asian – European American’ IAT). This IAT requires the ability to recognize White and Asian-American faces, and images of places that are either American or Foreign in origin.
Native American (‘Native – White American’ IAT). This IAT requires the ability to recognize White and Native American faces in either classic or modern dress, and the names of places that are either American or Foreign in origin.