The best source for information on Dorothy Day is the Catholic Worker website.
Some of her description of her mentor, Peter Maurin:
Peter made you feel a sense of his mission as soon as you met him. He did not begin by tearing down, or by painting so intense a picture of misery and injustice that you burned to change the world. Instead, he aroused in you a sense of your own capacities for work, for accomplishment. He made you feel that you and all men had great and generous hearts with which to love God. If you once recognized this fact in yourself you would expect and find it in others. [p. 171]
On voluntary poverty:
Going around and seeing such sights [of suffering] is not enough. To help the organizers, to give what you have for relief, to pledge yourself to voluntary poverty for life so that you can share with your brothers is not enough. One must live with them, share with them their suffering, too. Give up one's privacy, and mental and spiritual comforts as well as physical. [p. 214]
The shame activists felt when encountering poverty is part of their penance:
Over and over again in our work, many young men and women who come as volunteers have not been able to endure it and have gone away. To think that we are forced by our own lack of room, our lack of funds, to perpetuate this shame [of being stripped of all earthly and spiritual goods], is heartbreaking.
"Is this what you meant by houses of hospitality," I asked Peter [Maurin].
"At least it will arouse the conscience," he said.
Many left the work because they could see no use in this gesture of feeding the poor, and because of their own shame. But enduring this shame is part of our penance. [pp. 215-6]
The only answer in this life, to the loneliness we are all bound to feel, is community. The living together, working together, sharing together, loving God and loving our brother, and living close to him in community so we can show our love for Him. [p. 243]
We were like workers for a Utopia already living in their Utopia. We were dying and yet we lived. We were in sorrow yet rejoicing. [p. 247]
If it is remarked that pacifism places too much of a burden on the ordinary Catholic it can then be replied in truth that it places no so much a burden as does Catholic sexual morality with its day to day difficulties and the heroism it requires of many in these days. And yet the Church will not compromise in this regard. It would seem that the day must come when we refuse to compromise on this matter of war -- otherwise we will sink to sub-human bestiality and will most certainly stray far from the spirit of Christ. [Quoting Bob Ludlow, p. 270]