Arduino + motors multiple power supply setup

Hi,
I will have a Arduino Duemilanove. I plan to add 3-4 standard parallax servos and 2-3 vex motor modules to it.
My project involves powering the arduino and motors (plus some sensors) using wall power, preferable some modification of a wall-wart. And I cannot use batteries.

So I heard about the current limits to arduino (~500mA right?) and the need for separate power lines if controlling many motors. I bought a arduino motor shield to separate the supplies and do direction control.

Bu my problem is which/where do I get a power supply that can plug directly into both the arduino power jack AND the motor shield’s ext power terminal block. this would ideally plug into the wall like a normal adapter but just branch into two plugs at the end.

Plz help me find a part for this, I have no idea how. Or maybe I can mess with a normal 5V DC wall adapter’s insides to install another plug? :-/

I think the below is the connector I got that fit the barrel jack.

Tip size: 5.5mm O.D.x2.1mm I.D.

sorry i think Im not very good at explaining the problem.
I have a wall wart that outputs 5VDC & 1A. But since it only has one connection and its only suitable for plugging into a DC jack, I can't create separate power lines for both arduino and motors from that.

So my question is what kind of part CAN I use that will be compatible with both arduino DC jack AND my motor shield external power connection? I can't use batteries and must only have one supply powering both motors and arduino.

here are some of the parts Im using:
3 parallax standard servos
http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/servo/List/0/SortField/4/ProductID/101/Default.aspx
2 vex 3-wire motor modules, probably this kind Im not sure
http://www.vexrobotics.com/276-2163.html
this is the kind of shield Im thinking of using:
http://www.robotshop.com/ProductInfo.aspx?pc=RB-Ada-02

Please help. My project depends on it.

But since it only has one connection and its only suitable for plugging into a DC jack, I can't create separate power lines for both arduino and motors from that.

Why not? Don't you have any wire cutters? You do have a soldering iron, don't you?

um...I'm not very confident with power stuff. Can you show me exactly how I can modify the wall wart or solder stuff to create that second power line for motors. Do I need any other parts for this?

Then once I have that second power line, I guess I can just connect it to the ext motor power block on the shield?