Where can I find a good script for live customer support? Preferably free...

Try http://www.phplivesupport.com/

Good Luck.

is that one very good? do you use it?
are there any more?

I use http://www.phplivesupport.com and I recommend it the most. It is one of the cheapest and also one of the most functional.

If you can't afford the price that charge (18$ or so per month) you could probably download one from hotscripts.com or you might even find one on sourceforge.com