Skype lets you make cheap or free voice or video calls on computers running Windows, OS X, or Linux. There are even mobile clients available that let you make calls using your smartphone from a WiFi hotspot. But there's no official portable version of Skype that you can run from a USB stick.

It turns out though, that it's pretty trivial to convince Skype for Windows to run properly from a USB stick, which means you can save the program to a flash drive and carry it with you in your pocket. All of your settings and preferences will be saved to the USB stick, so your username, password, and other data won't be stored on your work computer, friend's computer, or other unsecure computer where you use the program.

Here's all you have to do:

1. Install Skype on your PC and then find the installation folder. It's probably something like "C:\Program Files\Skype." Copy the Skype.exe file to a folder on your USB flash drive.
   
2. In that same folder on your flash drive, create a subfolder called "data."
3. Create a new text file called "Skype.bat" or Skype Portable.bat" or whatever you like.
4. Open your new file using Notepad or another text editor and write "skype.exe /datapath:"data" /removable" (without the quotes).
5. Save and close your file

When you click Skype.bat, Skype should launch and all of your settings will be saved in the data folder. Although these instructions were designed for older versions of Skype and Windows, I just tested them with Wndows 7 an Skype 4.0 and everything works perfectly.

via The Portable Freeware Collection and ReadWriteWeb