Hey guys just wanted to mention the French website New Dreamarena.
I just discovered it but it was created back in December 2002. I must admit I'm quiet impressed with all the available options: a live Chat, a Forum, personal mailbox... There is also an English page, however the Chat does not work on it.
Apparently the community is almost dead. Some former French Dreamarena users sometime post messages but with a very low reply rate
Please note that I did not browse the site from a Dreamcast but I assume it's Dreamcast Browser Friendly. Also, you have to register yourself in order to get access.
I think it's a very nice project, especially if you understand French. I couldn't experience the official Dreamarena back in the days and reading all those nostalgic posts from French users is quiet touching.