Powered Rail

The Power rail will be added in Version 1.5. They will replace bug boosting (boosters will still work after the update).

It was tweeted by Jeb first to prepare texture pack makers where it will be.

It will have 2 states, powered and unpowered.

The tracks will be most likely made from gold, as suggested here:

 @jeb_ @notch What if instead of a booster glitch you have "golden" tracks that boost you when you go over it? Craft it with gold, not iron."

 "@War904 Hehe I kind of like that actually =)"

 "Sorry (3, 11) is powered, not (3, 12). Yeah power rails will either push or break (He meant brake ) carts, depending on if they are on or not"

 "@jeb_ Is the rail booster my golden track idea? If it is, awesome!"

 "@War904 Yep, it's golden!"

Jeb also tweeted about a Detector Rail. Which will act as a pressure plate combined with a minecart track, a normal pressure plate would slow the minecart but it will keep going over the detector rail.

Based on the above “golden track” conversation, the crafting recipe for power rails is probably: