Tributes have been pouring in on Twitter and other sites in tribute to Adam "MCA" Yauch of the Beastie Boys, who passed away earlier today. We've collected a few below.

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"There have been a lot of people who have molded the face and history of Hip Hop over the years, but no one can deny that my three dudes from New York City were paramount in taking it from a local thing and breaking it world wide. Last saw my man at the [Vh1] Hip Hop Honors Awards and he was upbeat, gracious and spiritual as always. R.I.P. to MCA...see you in the next one, brother." - Rakim, via HipHopDX.

"Adam was incredibly sweet and most sensitive artist who I loved dearly and was always inspired by his work. He will be missed by all of us." - Russell Simmons

"Adam Yauch as a young man may have been the 'Beastiest' of the Beastie Boys. Certainly, he was the angriest. In the wake of License To Ill, it was MCA who transformed himself the most. He evolved from his youthful punk rock anger into a peace-loving meditator. I personally was very inspired by his example." - Bill Adler, former executive for Def Jam when the Beastie Boys were on the label, told AllHipHop.com.