This isn't a very detailed history so if I am missing something you are looking for then e-mail me at sepulpan@slayerized.com and I will do my best to get the info for you.
-Late 1997- Former Sepultura front-man Max Cavalera assembled a group called Soulfly. Members-Jackson(Guitarz), Max-(Guitarz, Lyrical Terrorist), Marcello(Bassz), Ratta(Drumz).
-April 21st 1998- Soulfly released a self-titled CD. Singles off of this CD were: Bleed, Tribe and Umbabarauma.
-Spring 1998- Jackson left band to be replaced by Logan Madder from MachineHead.
-Summer of 1998- Toured with Ozzfest '98.
-Spring 1999- Released a Digipack with live recordings and remixes.
-Summer 1999- Logan left the band.
-Fall 1999- Ratta left the band.
-Fall 1999- Mikey from Snot joined as the new guitarist.
-Winter 1999- Joe Nunez from Fleshold joined Soulfly to fill in for Ratta's absence.
-Summer 2000- They replaced Ministry as co-headliners of Ozzfest 2000.
-September 26th 2000- Primitive is unleashed to the world.
-November and December 2000- Tour America with Primer 55, Slaves on Dope and Downset.
-Early 2001 American Tour with Pantera, Morbid Angel and Nothingface.
-October 2001 Drummer Joe Nunez leaves on good terms to join Chicago hardcore act Stripping the Pistol.
-November 2001 Former drummer Ratta replaces Joe as the new drummer for the upcoming album.
-Summer 2002 Soulfly 3 is released.