One of the most ambiguous aspects of Beckett's play is the identity of Godot. If the reader analyzes all the Biblical allusions, it is quite easy to say that Godot is God. (Actually, the word Godot can be anagrammed to say "To God," but it is questionable whether this is mere coincidence or has some significance.) The interpretation, then, would be of two men (mankind as a whole) waiting for something (salvation or proof) that will never come. (Every day, a messenger says that Godot will come tomorrow for certain.) This message is very appropriate when considering the play's existentialist aspects.
Interestingly, Vladimir and Estragon deny that they know Godot when Pozzo asks them. Keeping with the religious theme, this is parallel to Peter's denial of Jesus.
Another interpretation is that Pozzo is God, and Lucky is mankind. Perhaps Pozzo is really Godot, as he was mistaken for Godot, or maybe Pozzo is just there as a deception. Lucky wants to satisfy Pozzo with menial acts of obedience (according to Pozzo's own explanation of Lucky's actions), while Pozzo seems quite apathetic to Lucky's deeds and plights. However, in the second act, Pozzo needs Lucky to exist, because Pozzo is blind. Perhaps this is similar to the theory that God would not exist if man did not believe in Him.
Pozzo and Lucky are easily compared as the oppressed masses and the wealthy oppressors. If Beckett is trying to be a social critic, he could be saying that the oppressed are dumb and moored (Lucky is mute), or maybe he is merely showing humans at their most awful.
Mutual dependence is a recurring theme in the play....