Hi, it all depends what kind of live chat system are you looking for (how you're gonna use it). If you are looking a live support solution you can use:
- Livechatinc
- Live2support
- Providesupport
- Olark
etc.
For communities there are also a social chat solutions (including public and private chatting, users list, chat box) like:
- Chatwee
- Envolve
etc.
Regards