Heres an easy way to make your own cordless phone skype ready, Dont need to open your phone, and you can dial from it as well! All for about $5.

Props to Vitali Virulaine at http://www.vital.pri.ee/PSTN/ for coming up with, and sam for inspiring me to show him up, I hope you get into the maxim party!!!

Step 1: Parts Needed

-2 mini audio plugs 1/8" (buy cheap headphones and cut off the plugs)
-an RJ11 Plug (buy a cheap phone cord and cut off one end)
-2 100OHM resistors
-500OHM variable resistor
-2 3.3uF capacitors
-9V adapter, or USB plug, or use the one currently in your phone.

Step 2: Building

At first I was a little skeptical whether this would work or not, but I was pleasantly surprised when it did.
Connect the parts according to the schematic.
-I connected the grounds together and both left and right of the stereo plug together, since its going to be mono anyway.
-For the phone line cord, you use the center 2 wires only
-I didnt use a variable resistor, I used a 470OHM and it was loud enough
-Im currently powering it with my power supply, but will likely wire it into the phone's power supply. you could also run the wires to a usb plug and power it from your computer.

Step 3: Finishing.

If you have the skills you can make this into a nice PCB like Vitali did....

Step 4: Calling

Once your adapter is all hooked up, make a call to echo123 and make sure your sound and mic are working.

If you want to be able to dial from your phone, you will need to download the skype pluggin below.

You will need to calibrate this software to recognize your dialing volumes, just follow the wizard.
To make a call, pick up the phone, dial the number 15551234567 and press #
Alternatively, you can dial from skype.

Enjoy the freedom of your cordless phone!
Ive included a video of me calling from the phone as proof that it works!