“Aaron built surprising new things that changed the flow of information around the world"-Susan Crawford

"Aaron Swartz made a deep impression on everyone he met — whether it was his obvious brilliance, his cutting wit or his ardent dedication to issues concerning the Internet, public rights and civil liberties"-John Schwartz

Cory Doctorow remembered him thoughtfully in a graceful eulogy at BoingBoing:

"There is no way to express the sadness of this day," said friend, mentor, and Harvard law professor Lawrence Lessig. "There will be many words, eventually, to express its anger. This story will infuriate you. For now, to the co-creator of RSS, of the Creative Commons architecture, of part of Reddit, and of endless love and inspiration and friendships, rest. We are all incredibly sorry to have let you down."

"Aaron’s insatiable curiosity, creativity, and brilliance; his reflexive empathy and capacity for selfless, boundless love; his refusal to accept injustice as inevitable—these gifts made the world, and our lives, far brighter. We’re grateful for our time with him, to those who loved him and stood with him, and to all of those who continue his work for a better world.

Aaron’s commitment to social justice was profound, and defined his life. He was instrumental to the defeat of an Internet censorship bill; he fought for a more democratic, open, and accountable political system; and he helped to create, build, and preserve a dizzying range of scholarly projects that extended the scope and accessibility of human knowledge. He used his prodigious skills as a programmer and technologist not to enrich himself but to make the Internet and the world a fairer, better place. His deeply humane writing touched minds and hearts across generations and continents. He earned the friendship of thousands and the respect and support of millions more."-Official Statement from the Family and Partner of Aaron Swartz

I met him briefly in Cambridge and primarily knew him through interactions over social media and his writing. He was tirelessly devoted to sharing information online, particularly government and academic research and legal articles, a focus that embroiled him in controversy and courtrooms in recent years. Here's Swartz' Wikipedia entry, now updated:

As Declan McCullagh reflected this morning, "Swartz was facing possible life in prison because he allegedly tried to make journal articles public."

Gawker collected some of his references to depression: 

Gothamist's post on his death:

...ends with a coda I'll share here, in hopes that it will reach someone who needs to read it: "If someone you know exhibits warning signs of suicide: do not leave the person alone, remove any firearms, alcohol, drugs or sharp objects that could be used in a suicide attempt, and call the U.S. National Suicide Prevention Lifeline at 800-273-TALK (8255) or take the person to an emergency room or seek help from a medical or mental health professional."