Skype just updated it Skype fro Android App to support Samsung Galaxy S provided the phone is running Android 2.2 or later. Look for link below for how to upgrade you Samsung Galaxy S OS.
The update will also allow you ro store the Skype for Samsung Galaxy S on your phone's SD card (memory card). Even if the Skype for Android App is stored on the SD card, it will require internal memory to run the app, which Skype says will amount to 15MB for most users.
To get the updated Skype for Android App follow the link below or scan QR code, also below.
How to update Samsung Galaxy S phone
Get Skype for Android at skype.com/m