If you liked PostSecret, you may also like Barbara Kruger. Here's a description from a gallery of Barbara Kruger's work:

The juxtaposition of word and image in Barbara Kruger's highly recognizable work is derived from twelve years as a designer and photo editor for Conde Nast publications. Short, pithy caption-like copy is scattered over fragmented and enlarged photographs appropriated from various media. Usually declarative or accusatory in tone, these phrases posit an opposition between the pronouns "you" and "we," which satirically refer to "men" and "women." These humorous works suspend the viewer between the fascination of the image and the indictment of the text while reminding us that language and its use within culture to construct and maintina proverbs, jobs, jokes, myths, and history reinforce the interests and perspective of those who control it.

There's another gallery:

Barbara Kruger's on going project is to provoke questions about power and its effect on the human condition: to investigate the way power is constructed, used and abused. In her works, which have become the demonstrative visual icons of the 1980s and 1990s, power is interrogated and interpreted through the social, economic and political arrangements which motor the life impulses of love, hate, sex and death.

Kruger was also featured in the PBS documentary art:21.

It's our pleasure to disgust you is in the permanent collection at MOCA in Los Angeles.

In 2000, some of her art was shown at the Whitney Museum of American Art.

Here are some prints from the gallery of the Smithsonian American Art Museum:

We, Longer, Heard, Seen, And, No, Not, Be

A Slate article from July 2000 begins:

Barbara Kruger comes as close as anybody can to being the official artist of American consumerism.

An interview with Barbara Kruger:

By using familiar images and text from modern advertising, Kruger forcefully exposes the misleading and aggressive lies of pop media. Her works involve humor and irony, though they are often disturbing at the same time. Kruger gained her "fluency and comfort with pictures and words" from working as a graphic designer for magazines before she became an artist in the mid-'80s.

Barbara Kruger