Many Many Many people use the online chat server's which are available. The reasons for this become all to apperent when you end up with a busy community. There are so many services available I couldn't possible list them all here.
I use CHAT-FORUM whom provides JAVA chat room's & they can quite literally make you what you need. They do a free chat room, but by the scope of what you are looking for you should opt for a paid for service. Setup is approximately £100 and the monthly subscription is approximately £15.
I know your probably thinking this is quite costly, but bear in mind the benefits.
CHATFORUM host your chatroom, so wether you have 10 chatters or 1000 chatters you don't have to worry about bandwidth and how this would affect the performance of your website. They offer 3 standard services or a custom service. I have yet to find someone who is using the custom service. which mean they obviously cater for most senerios.
click here is an example of it's use
click here is where you can get your own chat room.