Yes. The article on the [Dark Side of the Force][1] on wookiepedia lists several organizations that exist in canon as users of the dark side:

**[Dark Jedi][2]**: Probably the most confusing group, Dark Jedi either were former Jedi who chose to follow the dark side or those with no light side training that simply chose the dark side. The difference between them and the Sith were the [specific teachings][3] of the Sith, however they occasionally worked along with the Sith.

**[Nightsisters][4], or Witches of Dathromir**: The best-known group of dark side users outside the Sith themselves. The dark side users of a shamanistic culture, they led the matriarchal tribes of Dathromir. Noted for riding rancors.

**[Rakatan Infinite Empire][5]**: The first known galactic government, they enslaved billions and used dark side powers to fuel their war machines and to create more with the Star Forge.

**[Prophets of the Dark Side][6]**: Technically a splinter faction of the Sith, this cult was founded by a renegade Sith Lord and eventually rose to some prominence under Emperor Palpatine.

**[Bando Gora][7]**: A dark-side worshiping criminal organization, singled out as a threat by both the Republic and the Sith.

**[Sorcerers of Tund][8]**: Reclusive group of dark side mages native to Tund. Rarely ventured off-planet.


  [1]: http://starwars.wikia.com/wiki/Dark_side_of_the_Force#Dark_side_organizations
  [2]: http://starwars.wikia.com/wiki/Dark_Jedi
  [3]: http://starwars.wikia.com/wiki/Sith#Philosophy
  [4]: http://starwars.wikia.com/wiki/Nightsister
  [5]: http://starwars.wikia.com/wiki/Infinite_Empire
  [6]: http://starwars.wikia.com/wiki/Prophets_of_the_Dark_Side
  [7]: http://starwars.wikia.com/wiki/Bando_Gora
  [8]: http://starwars.wikia.com/wiki/Sorcerers_of_Tund