artists whose work has a social/political massage
Adrian Piper (http://www.adrianpiper.com/)
Laylah Ali (http://www.pbs.org/art21/artists/ali/index.html)
Ellen Gallagher (http://www.pbs.org/art21/artists/gallagher/index.html)
Kara Walker (http://www.pbs.org/art21/artists/walker/index.html)
Gran Fury (http://www.queerculturalcenter.org/Pages/GranFury/GFGllry.html, http://www.creativetime.org/citywide/past_proj/granfury.html)

artists who work with text
Jenny Holzer (http://adaweb.walkerart.org/context/artists/holzer/holzer1.html)
Kay Rosen (http://www.kayrosen.com/)
Barbara Kruger (http://www.barbarakruger.com/)
Sheila Levrant de Bretteville (http://www.aiga.org/content.cfm?contentalias=sheilalevrantdebretteville, http://designwritingresearch.org/essays/sheila.html)
Guerrilla Girls (http://www.guerrillagirls.com/)

installation/performance/materials:
Do-Ho Suh (http://www.brown.edu/Facilities/David_Winton_Bell_Gallery/suh.html)
Ann Hamilton (http://www.pbs.org/art21/artists/hamilton/)
Kim Sooja (http://www.kimsooja.com/)
Bill Viola (http://www.billviola.com/)
Patty Chang (http://www.guggenheimcollection.org/site/artist_work_md_182_1.html)
Charles Ray (http://www.donaldyoung.com/ray/charles_ray_index.html)
James Turrell (http://www.pbs.org/art21/artists/turrell/)

Cultural Studies:
Stuart Hall (http://www.blackculturalstudies.org/s_hall/hall_index.html)
Judith Williamson (author of Decoding Advertisements)
Stuart Ewen is teaching in the Department of Film and Media Studies at Hunger College, CUNY. He is the author of influential books on the history of consumer society, visual culture, propaganda and modernity, including PR! A Social History of Spin, All Consuming Images: On the Politics of Style in Contemporary Culture, Captains of Consciousness: Advertising and the Social Roots of the Consumer Culture and, with Elizabeth Ewen, Channels of Desire: Mass Images and the Shaping of American Consciousness. Currently he is working on a multi-century study of the relationship between stereotyping and modernity, exploring the crossroads of art, science, mass media and popular culture, to be entitled: Typecasting: On the Arts & Sciences of Human Inequality.

These are some writers of graphic design culture:
Johanna Drucker (http://www.designwritingresearch.org/essays/drucker.html)
Ellen Lupton (http://www.designwritingresearch.org/)
Maud Lavin (author of Clean New World: Culture, Politics, and Graphic Design)
Rick Poynor( author: No More Rules: Graphic Design and Postmodernism)

Other interesting designers:
Ed Fella (http://www.edfella.com/)
Lorraine Wild (http://www.greendragonoffice.com/)
Edwin Utermohlen (http://www.doubledagger.net/)
Andrew Blauvelt (http://www.designmuseum.org/design/index.php?id=44)