Starting to get into Endless Universe: Beyond the Big Bang by Paul J. Steinhardt and Neil Turok. These two physicists put forth an alternative modifying the Big Bang theory, that of an endless cyclic universe, that is very compelling and creating a lot of talk. A summation is here- The Endless Universe: Introduction to the Cyclic Universe (ActionBioscience)
Other scientists who have played with the idea that I've read about seem to come to the conclusion that entropy increasing makes it impossible, but these two seem to have found the way around it; in their model, entropy does not build up.
I've always been kind of fascinated by some cultures' cyclic models of existence, Nietzsche's Eternal Return/Recurrence, ect., so this is pretty interesting for me. Though, an endlessly repeating cycle might not necessitate the Eternal Return (I saw a mathematical model which seemed to show that a finite number of particles in an infinite cycle would not necessarily have to repeat in placement). Still, it is an interesting concept to think about.