I believe, that it is within ourselves, rather than "out there" somewhere. That life as we know it is only the beginning of the journey of the "higher self" or spirit, or soul. "Science" acknowledges that "energy does not cease... it changes forms." I believe that it is this "change" that man has tried to define.
What we define as "heaven" or "otherworld" may be the extent that the human brain can comprehend this. I believe, that what follows "this place" is just out of reach of our understanding. "man cannot comprehend infinity" or "forever"
I do not believe in "ghosts". Even with the concept of resurrection (in the Jw definition) I believe there is flaw. The "dead" or "soul" is not aware of you anymore. It is in a state of change and growth. I always had a problem with people saying "we will see him/her in the new system". Do you think that when you grow to the next level of existence that you will remember what is here and now? Do you remember being the egg inside the falopian tube? ... no. Even christianity and the bible teach "that the dead know nothing". but not to say that they will not know.
Life has been an ever changing thing. Why do we believe that it will stop changing here? Billions and Billions of years have passed... an eternity..... and it will pass again. and again. But one thing has remained constant.... life changes. So in a sense I believe in the spirit world.... but not in a way that religion or science defines it. But the problem with religion... is that a group of people come together, and "WE believe" in a list of things. But ... you asked what I believe... and that about covers it.
*See... they screwed up my head after all. I broke loose at a young age, and I have spent my whole life trying to figure out the answer to that question.