I had a hankerin' to make a list but because this is a video game website, it will have to come in blog form.
 
This will probably change over time if I remember any.  Also some members of collectives will overlap.
 

• Native Tongues Posse
  - A Tribe Called Quest
  - Jungle Brothers
  - De La Soul
  - Black Sheep
  - Prince Paul
  - Leaders of the New School
  - Chi Ali
  - Queen Latifah
  - Monie Love
  
• D.I.T.C. (Diggin' in the Crates Crew)
  - Diamond D
  - Showbiz & AG
  - Buckwild
  - Lord Finesse
  - OC
  - Big L
  
• Hieroglyphics (includes the Souls of Mischief)
  - Del Tha Funkee Homosapien
  - Casual
  - Domino
  - Pep Love
  - A-Plus
  - Opio
  - Tajai
  - Phesto
  - DJ Toure
  
• Wu-Tang Clan
  - Gza/Genius
  - Rza
  - METHOD Man
  - Inspectah Deck
  - Raekwon
  - Ghostface Killah
  - Masta Killa
  - U-God
  - ol' Dirty Bastard
  - Cappadonna
  
• Soulquarians (non hip-hop members excluded)
  - ?uestlove
  - Common
  - Talib Kweli
  - Mos Def
  - Q-Tip
  - James Poyser
  - J Dilla
  
• Monsta Island Czars (M.I.C.) [unsure membership roster and collective name in parenthesis]
  - MF Doom (King Geedorah)
  - MF Grimm (Jet Jaguar)
  - Onyx (Rodan)
  - DJ Subroc (SpaceGodZilla)
  - Kurious (Biolante)
  - Tommy Gunn (Megalon)
  - (Kamackeris)
  - (King Caesar)
  - (Kong)
  - (Spiega)
  - (Gigan)
  - A bunch others I can't confirm