There is another plane known as the Twilight. It is technically "where the real meets the unreal". This plane is used often to manifest realities to yourself that art not yet, but you wish to come ("I will have a job"; in the Twilight, you see yourself obtaining a job). The Twilight Realm doesn't get near the...hmm--"publicity"--that the Astral Realm gets though. To get there is an O.B.E., but it you do not walk the planes of the Astral; you must focus on Chaos and a borderline real-unreal dimension and if done right you will be in the Twilight Realm. In this realm, there are other beings, but they are much stranger than Astral beings and this realm is a sort of "dim-lit" realm. To return from it, you do the same thing as when Astrally projecting: think of your body. Remember that Twilight Projecting can be used to bring about realities.
I am sure that there are other realms besides this one, but I cannot think of any off hand. Best of luck to you!
The only other things that may fall into this category are the different multiverses if you believe in the Infite Universes theory; in which case, you should look up Quantum Jumping and all the other "good-stuff" related to that theory.
well, astral is a bit of an all encompassing term. astral simply refers to the plane of existence. now within this plane are actual places, like Hell, Heaven, Underworld, etc.
now, there is also etheric (another encompassing term), Void, etc.
Keep in mind that Etheric is where the gods are. astral are where the lesser gods are at. in astral, there can be hundreds of deities that work together for the same effort. In etheric, there is no redundancy.
there is also the personal mindspace, and the human mindspace (Thunor's post). The human mindspace is linked to all the humans, so you can see that with all this stuff mashed together, it can be quite chaotic. Now, in mindspace, it takes immense effort to actually cause change. Mainly because it's your imagination :)
I belive in a large collection of planes. The plane of the dead is a notable one. I belive in a plane for each of the classic elements, spirit animals, a plane of regeration, and many more.
Yes. There is the real time zone, wich is a reflection of the physical world. There is also the mental planes, but projection to that is 99% of the time not remembered.