How to get Android ICS on Samsung Galaxy S:
Cyanogenmod which is an alternate ROM gives you the possibility to use android 4 (ICS) on your SGS (Samsung Galaxy S).
I tried the nightly builds from beginning of July and I had no troubles until now.
You can find all information about the ROM and about the „installation“ process on:
and the Wiki on:
I am using the CM9 until one week and I am very happy with the decision to upgrade to CM9.