I've seen this occasionally with some other games. Players will use hashtags to let others know, in real time, that they are available for a game. I'm thinking something like "#cosmicnow" or "playCE" might work.
Overall, it's probably still easier to use instant messaging to set up games, but not everyone uses the same service or is on the same friends list. So we'd need to start a user-name database or something for that to be effective ... hmmm, that could be a future blog post.
So, what say you, CE Online players? Does this idea have any legs?