8. A system comprising: a computing device; a network interface; non-transitory memory that stores instructions that when executing by the computing device are configured to cause the system to perform operations comprising: provide, over a network using the network interface, for display a terminal of a first user an avatar user interface configured to enable the user to at least: select an avatar from a library of avatars; assign a role in a presentation to a selected avatar; assign a voice to a selected avatar; receive, using the network interface from the first user terminal at least a selection of first avatar from the library of avatars, and role assignment, a first voice assignment for a first presentation, and a second voice assignment for a second presentation; cause to be presented on a terminal of a second user the first presentation of the first avatar speaking using the received first voice assignment, in the assigned role, using a first script, wherein the first avatar is animated and lips of the first avatar are synchronized with vocalization, using the first assigned voice, of the first script; cause to be presented on a terminal of a second user the second presentation of the first avatar speaking using the received second voice assignment, in the assigned role, using the first script, wherein the first avatar is animated and lips of the first avatar are synchronized with vocalization, using the second assigned voice, of the first script so that the user can evaluate the effect of voice on a listener.
8. A system comprising: a computing device; a network interface; non-transitory memory that stores instructions that when executing by the computing device are configured to cause the system to perform operations comprising: provide, over a network using the network interface, for display a terminal of a first user an avatar user interface configured to enable the user to at least: select an avatar from a library of avatars; assign a role in a presentation to a selected avatar; assign a voice to a selected avatar; receive, using the network interface from the first user terminal at least a selection of first avatar from the library of avatars, and role assignment, a first voice assignment for a first presentation, and a second voice assignment for a second presentation; cause to be presented on a terminal of a second user the first presentation of the first avatar speaking using the received first voice assignment, in the assigned role, using a first script, wherein the first avatar is animated and lips of the first avatar are synchronized with vocalization, using the first assigned voice, of the first script; cause to be presented on a terminal of a second user the second presentation of the first avatar speaking using the received second voice assignment, in the assigned role, using the first script, wherein the first avatar is animated and lips of the first avatar are synchronized with vocalization, using the second assigned voice, of the first script so that the user can evaluate the effect of voice on a listener. 14. The system as defined in claim 8 , wherein the system is further configured to receive over a network via the network interface a user's response to a query regarding whether the first avatar was more effective in the first presentation or the second presentation.