One interesting property of the new powered rails are that they act as brakes when no power is applied to them.
Because of this, you can make extremely simple stations like this one: ▮▓━─━═━─↔─ rail ━ booster rail▮
button ═ detector rail▓ any block
The minecart rests on the slanted powered rail because it the track acts like a brake.
When the button is pressed, the track becomes powered and boosts the cart away.
The sequence of detector, powered, detector track isn't a vital part of the station design, but is instead a 2-way booster.
When a cart passes over the detector track, the powered rail becomes powered, making a very compact booster.
This booster also helps push the cart up the unpowered slanted rail on arrival, resetting it for its next use.
I've been playing around with ways to make a cart magazine that isn't reliant on the cart boosting glitch.
However, it's not as simple as constructing something like this... ...
as additional minecarts will fall into the bottom one, melding together, instead of stacking.
YouTube user MinecraftAddict developed a hoizontal-cart-magazine-like concept using powered rails like this.
When the redstone is activated, each powered rail will send the cart to the next spot, while the final one will by launched to wherever you hook it up to.
However, simply using a button may power the rails for too long and cause some carts to move two spaces, so you may need to use a monostable circuit.
When the button is not pressed, the redstone torch on the side of the button's block keeps the output torch off.
When the button is pressed, the first redstone torch turns off, turning the output torch off.
At the same time, the repeaters have a redstone signal propagating through them.
When the signal finally reaches the output block, the torch turns off again.
By adjusting the delay time of the repeaters, you can adjust how long (short) you want the button press to last.
gaming.stackexchange.com/users/18/Kevin Yap
I did not make this, but I do not think a basic station can get simpler than this: ▮
▓┏━──
→ │
↑─ rail ━ booster rail▮
button ═ detector rail▓ any block
gaming.stackexchange.com/users/8581/James
I've been using the following design for a minecart station and have been very happy with it: I don't recall where I saw this design suggested, but it consists of a 1-by-3 trench filled with powered rails and a button on the wall above the middle rail.
When a minecart enters from either direction, it stops on the first downward-sloping powered rail it hits.
To keep moving in the same direction, you just have to hit the button, which boosts the cart back to full speed.
To reverse direction, you have to get out and push the minecart to the opposite slope.
It's a very simple design, although it does require a button click at every station in order to go continuously from one end of your minecart system to the other.
gaming.stackexchange.com/users/15/gnovice
→───═━─━━─━═───→ ..▮▮..
←───═━─━━─━═───←─ rail ━ booster rail▮
Button ═ detector rail.
redstone
The detector rail blocks push incoming minecarts in the middle section, where they are blocked in place by the unpowered booster rails.
Pressing the button powers all the boosters, sending and boosting the cart in the other direction.
gaming.stackexchange.com/users/8919/Casper
Another good method for use in a minecart station (particularly if you, for whatever reason do not wish to use the launch from an incline method) is to drop the minecart from above only to land upon the first booster rail track piece.
This is executed rather well in the video linked.
gaming.stackexchange.com/users/9796/Kris
With the advent of Minecraft beta 1.5 and  powered rails , I'd like to find designs of good "railway stations" so I don't have to babysit minecarts in getting them set up for launch down a rail line.  What's the best way to design a powered rail station?
How should I design a powered rail station?
gaming.stackexchange.com
<minecraft-java-edition>
gaming.stackexchange.com/questions/20394
gaming.stackexchange.com/users/190/fbrereto
The minecart rests on the slanted powered rail because the track acts like a brake. When the button is pressed, the track becomes powered and boosts the cart away.  Here is a similar, straightforward graphic set of buttons that will help you.
A set of similar instructions and buttons is provided by users.