I have discovered a few more new ROMs available since, and decided to add them to my list:
– Darky ROM: this one is quite known especially for SGS users, nice battery life, a few customisations, rooted ROM, it just entered beta.
– MIUI: Very similar ROM to cyanogen since it is build from scratch (gingerbread 2.3.4 sources on that release), it is still alpha for now as there is a list of broken things.
– Cognition S2: Rebuilt from official ROMs, rooted and customized, click on the link to see the list of changes.
A good place to take a look at latest development ROMs is at XDA.