(written from a Production point of view)
Alien Voices is a project involving a company of Star Trek (and other well-known) actors who come together to perform dramatizations of the great science fiction classics.
The project was formed in 1996 by Leonard Nimoy, John de Lancie and writer-producer Nat Segaloff. Having just come off of the collaborative effort that was the LA Theatreworks re-creation of the Mercury Theatre's War of the Worlds (for which Nimoy and other Trek stars performed, de Lancie directed and Segaloff wrote a modern-day extention entitled When Welles Collide), the three men decided to form Alien Voices to re-create other great works of science fiction literature for audio. These have included adaptations of H.G. Wells' The Time Machine, The Invisible Man and The First Men in the Moon (the last of which featured William Shatner as the Moon Emperor); Jules Verne's Journey to the Center of the Earth; and Sir Arthur Conan Doyle's The Lost World. They also re-created several of these productions in a series of three television specials for the Sci-Fi Channel.
The company produced two Star Trek audio productions focusing on the characters of Spock and Q: Spock Vs. Q and Spock Vs. Q: The Sequel. All of the Alien Voices audio productions have been released by Simon and Schuster Audioworks.
Unfortunately, the association between Nimoy, de Lancie and Segaloff appears to have been relatively short-lived. The project (apparently still active) has not produced any new material since 2000's Spock Vs. Q: The Sequel, and the official website maintained for the productions is no longer active. According to de Lancie,
- "The problem with Alien Voices was we had four really terrific years. And then it began to be about selling: Simon & Schuster wanted whatever, 40,000 units sold a year. And what we wanted to do was create really well-produced shows and have a library so that people in the future will simply know to come to an Alien Voices production that will always be good. And they didn't see it that way, and I thought, 'Oh my God, what am I doing? I'm going around peddling audio books! This is not what I want to do.' I loved writing them and directing them and doing them live, but I just didn't want to get involved any more." 
Several fan sites for the company do exist, including those listed below.