Many times I have seen people asking where is my for sale thread?

Answer: It is in a moderation cue...waiting to be approved or deleted or a request for additional information to make it meet Forum Rules (these rules are available for all to read, and believe it or not, the majority of you have clicked a box at sign up to verify that you have read them)
They can be found in red letters directly above the the thread you are reading, or any other thread you may read if any one is interested.

What is Moderation:

When there is a thread to be moderated, one of the mods opens and reads the thread and ensures that the ad contains information that the forum requires, the post count correct and so on...once we are satisfied that the details are all there, we hit the approve button...if there are details missing, we will most times approve the ad and request the other info be added.

Why does it take so long:

Simple, we are all volunteers and time is a commodity that takes a lot of managing, especially where there are family, work and other commitments we need to also take into account.

Sometimes it can take overnight or longer:

To true, but lets face it, it can take some members a week or longer to respond to a buyer requesting updates, or several days for the OP to adjust an ad that requires other info to make the ad compliant, and a lot of times we don't even get notified by the seller that the item has been sold or swapped.

I hope this explains a little better how the moderation system works and why sometimes it takes some time for an ad to be approved.