Chatroom?

I would venture to guess between 6pm and 11pm Central, from what I've seen. Also around 1 or 2am, when our neighbors across the pond are starting their days.
 
I also have found that 2 times are necessary. One for North America and one for Europe. Of course some lucky North Americans who work from home or can chat from work will be able to sign on in the early afternoon when Europe is just finishing dinner. :)

The flash chat puts a heavy load on my PC, otherwise I would leave it open like I do with my IRC chats.
 
Chatting

Bascially...it's a catch as catch can. If you are wanting to chat, one of the best things to do is to put yourself in the room. Then just go do something else on the computer but leave that window open with your sound on. As soon as someone enters, you'll hear the sound and then you can go back and chat. This doesn't always work (e.g. I've sometimes sat in chatroom and nobody comes in before I'm ready to leave) but the percentage is high to people coming in to talk.

Note...just being on the site doesn't seem to help much. You actually need to park yourself in chat.

Happy Chatting!
 
As I live in the UK, I normally catch people at 6 to 7 in the morning (in America, 1 to 2 in the morning). Sometimes I catch people just after nine to twelve at night (america - four to seven at night) sometimes ten (five).