Prison Arts Coalition is the first site I suggest you check out.
People write to me because I taught poetry at San Quentin in the 1980s through California's Arts in Corrections and in many prisons nationally since then. Here is some relevant material:
There's a long list of classic prison writers, but here are a few books by less well known people who are serving, or who have served, time:
Inside the Broken California Prison System by Boston Woodard
Mother California by Kenneth E. Hartmann
That Bird Has My Wings by Jarvis Masters
A Question of Freedom by R. Dwayne Betts
How You Lose by J.C. Amberchele
Wilderness and Razor Wire: A Naturalist's Observations from Prison and Time of Grace by Ken Lamberton
Teach the Free Man by Peter Nathaniel Malae
Here are a few of many excellent anthologies of prisoner writing:
Doing Time edited by Bell Chevigny
Couldn't Keep it to Myself and I'll Fly Away by the women of York Correctional Institution in Connecticut and edited by workshop leader, Wally Lamb
Prison Writing in 20th Century America edited by H. Bruce Franklin
This Prison Where I Live an international anthology of prisoner writing edited by Siobhan Dowd
Undoing Time edited by Jeff Evans
Wall Tappings edited by Judith A. Scheffler
Phyllis Kornfeld's Cellblock Visions is a beautiful collection of visual art made by people in prison.
Although materials and desire are all one needs to make art, there are an increasing number of programs through which people from the outside come inside to share. The Prison Arts Coalition website (linked to above) has information about and links to many of these programs. Here is another excellent source of information about programs and central issues.
Some programs are based in universities, some are nonprofits, some are government programs, and still others exist through church groups or because of dedicated individuals. Buzz Alexander's Is William Martinez Not Our Brother: Twenty Years of the Prison Creative Arts Project is a completely fantastic book in every way, including what it shows about what it takes to create and develop an outstanding program.
PEN has an annual prison writing contest and offers many ways for writers on the outside to work with writers on the inside. The program also offers a Handbook for Writers in Prison and Words Over Walls: Starting a Writing Workshop in Prison.
Many who have worked inside have written about the experience. Some of these books combine the writing of prisoner students and their instructors. Three of these are:
Teaching the Arts Behind Bars edited by Rachel Marie-Crane Williams
The Funhouse Mirror: Reflections on Prison (Robert Ellis Gordon)
The Soul Know No Bars: Inmates Reflect on Life, Death, & Hope (Drew Leder)
There are also memoirs, such as my own Disguised, and other nonfiction descriptions. Here are two of my favorites:
True Notebooks: A Writer's Year at Juvenile Hall by Mark Salzman, is a wonderfully well written account.
Crossing the Yard: Thirty Years as a Prison Volunteer by Richard Shelton, so good and full of fury and heart.
Some books refer to what artists teaching inside have learned about our criminal justice system from seeing prison close-up:
Challenging the Prison Industrial Complex: Activism, Arts, and Educational Alternatives edited by Stephen John Hartnett
Performing New Lives: Prison Theater, edited by Jonathan Shailor
America Is the Prison: Arts and politics in Prison in the 1970s, Lee Bernstein
Michelle Alexander's The New Jim Crow exposed the racism at the heart of our criminal justice system and has had enormous impact on people and policies. Here are some less well-known books that also address the history (both long-term and more recent) of mass incarceration.
With Liberty for Some: 500 Years of Imprisonment in America by Scott Christianson
The Rise and Fall of California's Radical Prison Movement by Eric Cummins
Going up the River: Travels in a Prison Nation by Joseph T. Hallinan
Cruel Justice: Three Strikes and the Politics of Crime in America's Golden State by Joe Domanick
When Prisoners Come Home: Parole and Prisoner Reentry by Joan Petersilia
All Alone in the World: Children of the Incarcerated by Nell Bernstein.
Die Jim Crow is a quite amazing project inspired by Michelle Alexander's book.
One consequence of these past decades of mass incarceration has been children with parents in prison. Community Works, in the Bay Area, has many programs for youth whose lives have been impacted by prison -- many of these involving art-making. And POPS (Pain of the Prison System) is an amazing school club in Los Angeles that invites young people with family and friends in prison to share with each other. POPS publishes writing and artwork by participating youth.
There's a long list of prison activist groups. Here are a few: