Unlike Mason at 2+2, I don't have a paranoia regarding spam. That is, I don't care if you want to post links to other sites (or even your own site), even if somehow the site will benefit for free from that link.
The only requirement is that you need to have a reason to post the link (or the ad) other than strictly trying to advertise.
So, for example, the post I made about PokerSnowie over in the Poker Community forum is okay (even if it were written by someone other than me), because it's discussing an interesting topic of whether bots can successfully train you to be better at NL.
However, I don't want to see ads here such as "Get a free $5 to sign up at this site" or whatever. If you want to advertise like that, you have to pay for it.
Thank you for your cooperation.