Rakim was part of a duo called "Eric B. & Rakim".
You can hear Fred Durst of Limp Bizkit repeating some lines of "Crawling" from the second day of Rock Im Park 2001.
NoBraiN also did additional production on "When They Come For Me".
Stephen Carpenter of Deftones plays guitar on "By_Myslf".
Doug Trantow was programmer, producer, and engineer on "Pts.OF.Athrty".
Roc Raida (X-Ecutioners) on "X-Ecutioner Style".
Sean C. (a DJ) produced "X-Ecutioner Style".
Greg Kurstin of The Bird and the Bee plays keyboards on "MyMichael Fitzpatrick of Fitz and The Tantrums worked with Mickey Petralia on "My
Edit:
If you want to add J. Robert Oppenheimer, Mario Savio and Martin Luther King, Jr. you would have to add Mr. Eon of The High & Mighty (for She Couldn't), the guys from Brand Nubian (for H! Vltg3), etc...
I agree with xLinkinpark0562x. We shouldn't list samples.
Edit 2:
We have 2 titles for the Does It Offend You, Yeah? remix of The Catalyst:
The Catalyst (''Bobby Bloomfield'' DIOYY? Remix)
- The Catalyst EP
The Catalyst (''Guitarmagedon'' Does It Offend You, Yeah? Remix)
- Waiting For The End single
From the first title, we can assume only Rob Bloomfield worked on the remix.
Edit 3:
Remix.