Who sent/left Commander Adama the message at the end of the mini-series that reads:
“There are only 12 Cylon models.”
It hasn’t been revealed yet.
That’s going to upset the collectors.
Had to have been Baltar, becausehe was the only human who knew - Six told him in bed back on Caprica.
No it doesn’t. It could just as easliy been Galactica-Boomer, or some other Cylon sleeper agent
Escept that G-B wasn’t online yet, and even if she was, she’d have no reason to tell Adama. But on this show you’re never quite sure of anything, and that’s a huge part of its enjoyability.
No kidding. For all we know Adama could turn out to be the Imperious Leader, complete with Christmas Tree lights in his head! 
We don’t know how long G-Boomer has been doing things. Remember, apparently being a Cylon sleeper Agent is a lot like having Tyler Durden for a best friend. If he does something, you won’t remember it. And sending a message is a lot less notiable then waking up soaked next to a half-empty box of detonators just before a water tank explodes
I read somewhere (maybe in Ron Moore’s blog on scifi.com) that they originally had Baltar as the one leaving the note, but as they were editing the miniseries, they realized it would be a lot more interesting if they left it unresolved, as it would give them lots of options for the coming series. I hope they haven’t forgotten about it.
(The first season seems to be occupied more with introducing plot threads than with tying them up, a habit that will become somewhat irritating if they leave too many interesting questions in the dust, the way X-Files did. So far it’s fun, but there are some small danger signs in the margins.)
Did anyone else think:
that every entry in this thread would have something written in a spoiler box?
Yes.
It was the one-armed man!