What kind of bicycles do they ride in the Tour de France? I've been looking at a lot of the coverage of the Tour de France. All of the attention is on the cyclists, and no attention whatsoever on the cycles. Even in photographs or videos, they are so far away, or the bikes are moving by so fast, you can't tell what they are riding.

I know I definitely can't afford whatever kind of bike they are using, and it would be horribly impractical for me to ride one since I'm commuting, not racing. I'm just very curious as to what is the top of the line in terms of bikes. When I look at high end bikes in shops or online I can't tell if they are actually superior or if they are just loaded with expensive gimmicks.

What frames, brakes, seats, gears, tires, etc. are the world's top competitors using?
The focus is on the riders, because the bikes are just not so different from one another. The UCI (international cyclists' union) tightly regulates what shape and weight the bike must be, and what technical solutions are acceptable, so the sponsoring manufacturers can only compete on relatively minor features such as aerodynamic tubing or frame stiffness. These are of no practical importance to an everyday cyclist.

A typical racing top-level bike nowadays will have 


an aluminum or carbon fiber frame, with increasing focus on aerodynamics over weight (because it's relatively easy to achieve the UCI minimum weight of 6.7kg regardless)
always a carbon fiber fork
either super light or aerodynamic wheels, depending on the type of rider and needs of the particular stage 
either Campagnolo Super Record, Shimano Dura Ace, or SRAM Red component set, depending on who's the sponsor