I don't know, communication isn't so great, I have no idea which sites are officially banned, which have bans lifted. There may be a spot on the reddit blog or somewhere else that I'm not aware of but really it shouldn't be my responsibility as a user to enforce it that's the job of admins and mods, that's why they exist.
It doesn't seem to matter though because I have seen banned websites post even when they are supposed to be banned, reddit doesn't seem to block the url it just mentions the website is spamming reddit and that seems to be all we're told.
There is an unofficial (?) subreddit that monitors of banned websites, look to the right at the sidebar for the link to the list http://www.reddit.com/r/BannedDomains/
It doesn't seem to matter though because I have seen banned websites post even when they are supposed to be banned, reddit doesn't seem to block the url it just mentions the website is spamming reddit and that seems to be all we're told.
There is an unofficial (?) subreddit that monitors of banned websites, look to the right at the sidebar for the link to the list http://www.reddit.com/r/BannedDomains/