In addition to the discussion on ideologies in Critical Theory & Practice (124-34), you might find James H. Kavanagh's comments on ideology helpful:
Ideology is less tenacious as a "set of ideas" than as a system of representations, perceptions, and images that precisely encourages men and women to "see" their specific place in a historically peculiar social formation as inevitable, natural, a necessary function of the "real" itself. . . . there is no such thing as social discourse that is nonideological. . . . Ideology is a social process that works on and through every social subject, that, like any other social process, everyone is "in," whether or not they "know" or understand it. It has the function of producing an obvious "reality" that social subjects can assume and accept, precisely as if it had not beenb socially produced and did not need to be "known" at all. The "nonideological" insistence does not mark one's freedom from ideology, but one's involvement in a specific, quite narrow ideology which has the exact social function of obscuring--even to the individual who inhabits it--the specificity and peculiarlity of one's social and political position, and of preventing any knowledge of the real
processes that found one's social life. ("Ideology" 310-12 Critical Terms for Literary Study)

Klages on Marxism

Klages on Althusser