From StarWars.com:
"Since her debut in The Clone Wars, Asajj Ventress has captivated fans with her lithe look, seductive aura, and deadly skill with two lightsabers. Giving voice to a character which is quickly becoming a fan favorite of the series, Nika Futterman brings a seething and sultry quality to the role of the notorious Sith apprentice.

We asked Nika a few questions about her role as Ventress, and of the intriguing relationship she seems to share with Obi-Wan Kenobi..."

See also:
Voice Of The Clone Wars: Terrence "TC" Carson
Voice Of The Clone Wars: Matthew Wood