Forum 7
Forum 7 was skipped in the numbers of publicly visible forums on the old NationStates forums before the switch to Jolt. There was a forum 6 and 8, but not a 7. Players speculated out that it had to be a forum that only moderators could see, but that didn't stop a conspiracy from developing. In fact, many conspiracy theories were formed around this mysterious "Forum 7."
On April 1st of 2004, Max Barry created a public forum entitled "Forum 7" which remained public until the switch to Jolt. This forum was home to more conspiracies and quote temples (quote pyramids - made out of many blank quote messages). Another, deeper, conspiracy developed as it was found that "Forum 7" was really numbered 13.
There is also a Forum 7 (region).