As surprising as it is, considering we're still more than a month away from Fallout: New Vegas release, Playstation Blog published a complete list of the New Vegas companions, including screenshots and their ages, races and bonus perks.
Be warned spoilers that it contains minor spoilers.
You can also read our very own articles about the companions, which in some cases have extra information from various previews and interviews:
Remember that you have two companion slots in the game - one humanoid and one non-humanoid.
Update: IMDb already has the voice actor listed for one of the newly announced characters - David Anthony Pizzuto will voice Lily Bowen (for some reason misspelt there as "Lilly Borden"). We also know that child actor Sam Cohen will voice an unspecified character or characters (probably the game's children).