If there was a big bang, or as others say a little bang followed by a big bang, nothing would be immobile at that point in space. It would all be speeding away from that center point.
Sort like the waves rolling away from the place where a pebble is dropped in water.

Is there an ever-expanding void at the center of our universe? If so, would it simply be empty space or would some type of anomly be there caused by the huge expanse of energy released in the big bang?

if you believe the "big-bang" theory, there should logicaly be a huge and expanding void and emptiness in the center of our universe.

If you buy into the Big Bang as being a solid, respectable theory - then, well, there's not much that can be done for you.

In any case - no one can really claim to tell you what happened at the beginning, or even begin to wrap their brain around "expansion." Math goes out the window as we cannot assume modern precedents applied during that time - so you can't really listen to a mathematician talk about the Big Bang and give it any more credit than "interesting idea."

There's nothing to indicate the "big bang" has stopped - or that it was a single, isolated event (I'm more of the opinion that the "bang" was more of a "rip" or "wave" that released energy over time to create the fibrous distribution of galaxies and clusters we see today).

However, making several large predictions, the point where everything came into being and sped away at faster-than-light speeds as the fundamental forces came into existing, would either exist as a perfectly 'flat' region of space - all gravitational fields canceling each other out, or not really exist at all.

If you accept the idea that the fundamental forces had yet to really come into existence - and space is 'created' by mass/gravity - then the space we inhabit did not really exist until long after the initial release of energy. There would, then, have to be two events. The "bang" - which created its own concept of existence, before 'dropping' into our universe after losing energy to some other process.

Of course - remember what I said earlier - you can't put much weight behind any theory of the "big bang." I still entertain the notion - but I believe it is indicative of people attempting to make science fill the roles of religion. We want to try and answer the question "Where did we come from" so badly as to forsake responsible scientific practices and guard a poorly-constructed model of the answer to that question with a religious fervor, elevating it to the status of a deity in and of itself.

I look forward to the day we try and explain to extra-terrestrials the origin of the universe (as the Big Bang) in the belief they came to the same conclusion - only to be laughed out of the room (or, whatever they do as a response to something they find humorous).