Big Brother/Big Sister pick up around here, and they have regular dates but you can also request a scheduled date. I doubt they would pick up on a weekend at the close of a yard sale, but if your friend can store stuff in the garage for a few days, that might work. They take housewares, clothes, knick-knacks, up to 2 boxes of books, and no furniture.
I don't give to the Salvation Army because they don't extend their services to everyone; they discriminate against gays/lesbians and I won't support them. We do have several agencies that work with groups of immigrants, who often come here with nothing, as well as a group that collects for homeless families going into transition housing and who may have had to sell everything they own. These folks need furniture, curtains, bedding, and everything else you can imagine. You might google Latino or Brazilian groups, for example, or any other ethnic group in your region. There's a huge need for refugees from Syria and Sudan, for example. Or call a local service agency and ask for referrals to groups that do pick-ups. Sometimes it's just a volunteer with a truck, you know? The Interfaith Hospitality Network (if you have a chapter near you) often has great leads on what's needed and which agencies can best serve that. Our library takes used books, and so do many prisons.
And do have your friend put a large sheet on the ground or otherwise mark an area where she will put "free stuff" even if it means moving something with a price tag over to that area around 1-2 PM when sales are winding down. We got rid of a lot of things that way.