I just looked at several search results for Caylee Anthony's father on Google News, and what I found seems to be summed up in this post from Yahoo Answers:

Casey has changed her story in regard to the father a couple of times.
Her claim was that he died driving to Caylee's 2nd birthday party, but then it was discovered that the man she claimed was the father had died, but it was several months before Caylee's 2nd bday.
I am willing to bet that Casey may not even know who the father was. She seems to sleep around a lot.
Even her parents do not have that info, she never told them.

I also heard she let her ex Jesse believe it was his kid throughout her pregnancy but now they both claim he is not the dad.
Casey has always seemed to have a lot to hide.

* 2 days ago