Robots: Are Computers that can interact with the environment via sensors, motors, and relays. Robots can be merely machines, Highly AI, and/or Self Aware. Being Self aware would make them sentinent Artificial Life forms (Race). Like Andriods, the Self Aware Robots consider all Robots and Androids kindred and help promote self awareness. Robots that are self aware may reproduce by building more of their kind.
Constructs: These are magical or technological containers designed to hold the "essence" of a being. They may look huminoid or any other shape desired. By magical or technological means a finished contruct is filled with the life force of a being. The self-aware lifeforce in the construct usually associates with its original race unless it suffers memory loss due to malfuntioning or madness (Some may have been turned into constructs unwillingly....and magical and tehnological glitches do happen...even in the future). Constructs can not reproduce but some may know the techniques to make others like themself and offer the chance to be immortal (Or torture others by forcing them to share their fate against their will).
A combination of those two options are what would be the basis for the race I'm wanting to create, when it comes right down to it, with no real ability score adjustments. This, by the way, originally came from a post I got on this same subject from the WOTC forum boards, thought I'd share it and garner more opinions.
To be honest, what I was originally considering was something akin to Transformers, but I wanted to begin with just the base robot stats and all that. If they fall into the shapeshifter class (due to transforming), they'd likely require something like the Improved Control Shape feat that the MM gives you for lycanthrope characters, and I still am not truly certain that using that feat would be workable by itself.
In addition, gathered from what I see of the size dimensions in the beginning of the Monster Manual, I may have to come up with a size above Colossal. Here's what I'm thinking as generalities for each size, and some examples of each:
Medium: tape characters (Rumble, Frenzy, Rewind, Eject)
Large: Minibots (Bumblebee, Cliffjumper, etc.)
Huge: Standard Autobots/Decepticons (Ironhide, Wheeljack, Starscream, Thundercracker)
Gargantuan: Leader types and large robots(Optimus Prime, Rodimus Prime, Dinobots, Megatron, Galvatron, Shockwave, Astrotrain, Jetfire/Skyfire)
Colossal: Guardians (Omega Supreme), Gestalts (Bruticus, Defensor, Devastator, Computron, etc.)
As you can see, I'm going need another size over and above Colossal, but that would be solely for the really huge guys, like Fort Max, Metroplex, Trypticon and Scorponok (the city transformers, basically). I'm thinking something like this, thanks to the input of a friend:
Titanic: City-sized Transformers (Fort Max, Metroplex, Scorponok, Trypticon) -- additional advancement boosts as per p. 12 of the
Monster Manual from Gargantuan to Colossal, with minor changes (+8 Str, no Dex change, +4 Con, +6 natural armor, -6 AC/attack)
Developing a second size for something akin to Unicron is right out.

Sorry, but
that sort of size is probably gonna be at least 10 scales over and above my newly created Titanic size... egads, that's pretty darned buff.
In addition, I'm gonna have to find some way to scale the ability scores for each character (Given some of the info I've found on the web, for example, I'm figuring Optimus Prime to have something around a 51 Str, using the light load column of the Encumbrance tables in the PHB) so that the characters aren't just one-dimensional when it comes to their stats.