The new issue of Popular Science Magazine features this way-cool article (which the writer and editors tie into next month's IRON MAN movie) about real-life projects dedicated to developing exoskeletons that can perform many of the functions that IM's armor can in the comics. These prototypes can't fly, or fire plasma weapons from their palms; but they can augment the wearer's strength and endurance. Here's a video of the XOS suit in action.
Beyond the obvious military applications (the projects were started by Darpa grants, and one of them has won a grant from the U.S. Army), these exoskeletons may one day allow the crippled to walk, and let heroes like fire-fighters become real life superheroes.
In the comics, one of Iron Man's constant challenges was maintaining his exoskeleton's power supply; and these real-life armors face the same challenge. Right now, the most promising powersuit resembles one of Neon Genesis Evangelion's Evas in that it requires an external power source (and an extension cord). Making the suits self-powered doesn't require increasing battery power so much as decreasing the suits' power demands.