The fundamental link between knowledge/belief/utterance and material/political interests and position in social space is arguably among the most provocative contribution of the social sciences to human knowledge. Unfortunately "ideology" is thrown around with such abandon that it's easily detached from meaning anything in particular. This sampler takes us through some classic examinations of what ideology is, how it works, and how authentic discourse can exist in the face of it.
Mannheim, Karl. 1936, 1929. "The Sociology of Knowledge and Ideology" (217-221)
Bell, Daniel. 1960. "The End of Ideology in the West" (291-294)
Althusser, Louis. 1968-9. "Ideology and the Ideological State Apparatuses, Doubts and Reservations" (321-324)
Gramsci, Antonio. 19xx. "Intellectuals and Hegemony" (263-265)
Habermas, Jürgen. 1968. "Emancipatory Knowledge" (386-7)
Habermas, Jürgen. 1970. "Social Analysis and Communicative Competence" (387-9)
Berger, Peter and Thomas Luckmann, Society as a Human Product" (390-4)