Just about every culture in human history can be identified as having religious practices and beliefs. Why is that? What is it about humanity that leads us to search outside ourselves for meaning/hope/whatever else religion provides?

Well, I have thought that relgion has come from a need to understand the natural world around us. Religon offers an explainiation of the things natural by use of the super natural. This is also why religion has evolved over the years, from many gods and explainations of the world's universe's turning to now adays, explainition of our roots and other things that we still cannot explain on our own.

I agree with Delta's statement that religion is used to fill in all the gaps in our understanding of the universe.
Then, of course, there's always that idea that religion was created to control the masses, to make them fear standing up to authority. To an extent, I believe that this is right. Originally, people helped start religion to control others. Is it still the same way today? I can't vouch for anywhere else, but it has pretty much died out in the US. Obviously, there are still those nut jobs fundamentalists, but I believe that religion has a lot of personal importance, and for that reason, I believe religion to be a very good thing.
But, I also believe that religion came into being because of a more spiritual kind of reason. People want to believe that there is someone watching over them. They want to believe that they will be safe. They want to believe that they will live on forever. I understand feeling very well. It is one of the reason's that I believe in some sort of afterlife. I want to believe that the people I know and love aren't gone forever. I want to believe that someday, I will see them again. I know it can be silly to believe such a thing, especially when, in all honesty, I find it hard to believe in such a thing... but there is something deep inside me that wants to believe. As I said, I don't want this life to be the end. Even if I don't make it to Heaven, I want those I know and love to be happy and live forever. Maybe that's why I believe.

I agree that religion had some of its roots in the desire to explain the unexplainable, however, I do not feel that it is enough. For example, there are scholars who believe that the Jews didn't have a creation myth (the first few books of genesis) before meeting up with some Phonecians and hearing their creation myth and talking to them about their gods, when the Phonecians asked them about Yaweh they answered, but couldn't explain where everything came from, and so the creation myth in Genesis is the answer to those early conversations...

I feel there is a drive that Freud didn't talk about, a spiritual drive if you will, a push towards the divine, towards finding something "meaningful and fulfilling"

Freud talked plenty about that drive, but he didn't consider it a drive like the libido or like the death drive.

He might agree with you Boru, that religion does not necessarily come about primarily simply to explain things, although he would agree with deltasix that this is indeed part of it all. In Freud's view, religions basically come from our weak egos. In the monotheistic traditions, the source is a fundamental neurosis of fear--we fear the unknown, we fear death, we fear life! And when we learn that our parents can no longer comfort us from these things, we create the ultimate parent--God--who not only comforts us in life but shields us from death. In eastern traditions, say like Taoism and Buddhism, Freud would probably argue that the drive for "enlightenment" reflects a fundamental desire to return to our most basic state of egolessness, since it is the ego that causes our anxiety to begin with.

I'm not sure how to answer this question myself, but I have a feeling it has something to do with the other question about what common ground religions share.