There has been news lately saying that the universe may not be infinite in size, but could be only about 70 billion light years across. Space wraps around so that light from a galaxy would eventually come back to where it started. Somehow they figured this out by observing the background microwave radiation of space, but I don't understand exactly what their reasoning is.
Anyway, it's very interesting that we may soon know whether the universe is finite or infinite in size. Here is an article about this:
http://www.newscientist.com/news/news.jsp?id=ns99994250