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. 
R I P Adam... I'm devastated.Praying for Adam Yauch's family from the legendary Beastie Boys. Youll be missed!
- Rev Run (@RevRunWisdom) May 4, 2012 
Yauch is gone. f--k.
- Questo of The Roots (@questlove) May 4, 2012 
"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 
RIP yauch and thank u mike and adam n adam 4 all of your help, the tours, the bball games, n great times. a humanitarian a tru friend
- QTip (@QtipTheAbstract) May 4, 2012 
RIP Adam Yauch of the LEGENDARY Beastie Boys ... damn.
- Estelle (@EstelleDarlings) May 4, 2012 
- ASCAP (@ASCAP) May 4, 2012 
RIP adam, so many great memories of you and the beastie shows we all did together
- KevinLyman (@KevinLyman) May 4, 2012 
R.I.P. Adam Yauch - Beastie Boys. We've lost a visionary artist. Sitting in Brooklyn and feeling the impact like a black cloud.
- Amanda Palmer (@amandapalmer) May 4, 2012 
- Def Jam Recordings (@DefJamRecords) May 4, 2012 
I feel weak. TMZ: Adam Yauch, MCA from the Beastie Boys is dead at 47.
- Touré (@Toure) May 4, 2012 
Rest In Peace Adam Yauch /MCA. 4ever somebody i looked up to & had the pleasure of meeting. Damn this bums me out, we lost one of the best
- Travis Barker (@travisbarker) May 4, 2012 
Man. I was raised on the Beastie Boys. They were (and will always be) heroes for me & my bro. Soooo sad. #RIPMCA 
- A-Trak (@atrak) May 4, 2012 
Adam Yauch was an amazing artist and one of the nicest people I've ever met. His music was some of my favorite. Truly saddened. RIP MCA.
- Donald Glover (@DonaldGlover) May 4, 2012 
so so sad about MCA gone but never forgotten your music will live on forever in our heads. ur first album was my soundtrack in high school
- Gary Richards (@DestructoHARD) May 4, 2012 
"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. 
RIP Adam aka MCA...we will continue to Fight for our Rights...prayers and blessings from your original Def Jam family
- Kevin Liles (@KevinLiles1) May 4, 2012 
RIP MCA U are a Legend and a pioneer. #BeastieBoys4life 
- Snoop Dogg (@SnoopDogg) May 4, 2012 
Rip dear Adam Yauch. Words can't express the sadness and loss. Ur humor, talent & gentle soul are just irreplacable. Be at peace brother.
- Tom Morello (@tmorello) May 4, 2012 
A VERY SPECIAL R.I.P. TO ADAM YAUCH FROM THE BEASTIE BOYS MY BROTHER YOU ARE GONNA BE TRULY MISSED MY HEART IS HEAVY.....
- BIZ MARKIE (@BizMarkie) May 4, 2012 
Brass Monkey was the worst tasting liquor ever. And we drank it anyway. Cuz the song was so jamming. RIP MCA. #BeastieBoys4Life 
- Bun B (@BunBTrillOG) May 4, 2012 
Crushed to hear the news of Adam Yauch's passing. A true pioneer of art. My thoughts and prayers are with his family and loved ones. #RIPMCA 
- Justin Timberlake(@jtimberlake) May 4, 2012 
- Chuck Schumer (@ChuckSchumer) May 4, 2012 
R.I.P. Adam Yauch Beastie Boys #RIPMCA 
- MC HAMMER (@MCHammer) May 4, 2012 
Struggling to find the words to describe the grief I feel over the passing of MCA. We love you Adam.
- Talib Kweli Greene (@TalibKweli) May 4, 2012 
Mca Adam Yauch RIP... Im sittin in the former g son studios.. Flying the flag half mast today.... Rap/punk hero, philanthropist, legend
- dÃ"Â±pÃ-ÂŸo (@diplo) May 4, 2012 
Rest in peace MCA of the Beastie Boys. A pioneer, legend & OG that will be missed.
- Big Daddy Kane (@officialbdk) May 4, 2012