Taylor Swift is still standing up to cancer, as proceeds from her touching song, "Ronan" -- which hit No. 1 on iTunes over the weekend -- are going directly to various cancer charities. (Download it here.) The music superstar sang the new tune on last week's multi-network "Stand Up to Cancer" television event, choking back tears at the end of her performance. (Watch below.)

Taylor shares writing credits for "Ronan" with Maya Thompson, who lost her 4-year-old son, Ronan to cancer last year. The singer-songwriter was inspired by the grieving mother's "Rockstar Ronan" blog, on which she writes poignant, tearjerking letters to her late son, while at the same time raising money and awareness for childhood cancer causes.

Tim McGraw also performed a moving tribute at the "Stand Up to Cancer" event, singing his mega-hit, "Live Like You Were Dying," on the live broadcast. That song was Billboard's No. 1 country hit of the year in 2004, which was the same year the country superstar's father, Tug McGraw, died of cancer.

Watch Taylor Perform "Ronan"

Watch a Video on the Stand Up to Cancer TV Event

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See Photos of Music's Cancer Survivors