I just checked the profile for Jaymin, who started this thread. I was hoping to get a sense of where this person was coming from in asking that question.
I run a successful niche directory and so I certainly have a bias, but I think that all of this talk about directory quality is off the mark, when it comes to the topic of this thread. Seems to me the answer to Jaymin's question is, "Why bother?" Just submit your site to the free directory and don't be concerned about it. Seems like everyone here agrees that there isn't much to lose by doing so, right?
That said, I can't help but chime in on what I think makes for a free directory worth submitting to. I ask myself these questions:
What are the chances of it making money for me?
If it works, can I do anything to stand out and get more traffic from it?