Having problems connecting your Samsung Galaxy S to your Ubuntu PC? I had the same problem, and the solution (which I found here) is a joke.
SOLUTION: In Settings > Applications > Development, change the setting “Stay awake” to “on”.
Your device will pop up as an external drive in Ubuntu when you try to connect as a mass storage device.
“Stay awake” is supposed to make the screen stay lit when the phone is charging. If anyone knows the logic behind all this, please tell me.