It depends on what ``we'' and our ``universe'' happen to be.
In the materialist viewpoint, there's just the universe and that's axiomatic - you don't ask what it is.
There is another popular viewpoint - the universe is just math viewed from the inside - you can see this in the writing of Max Tegmark, Schmidhuber, Bruno Marchal and so on.
Now the question becomes, "which math?" and "what is consciousness?"
Tegmark initially considers all consistent math, but that has its own problems, so his current position is limited to only computable ones. Schmidhuber considers an Universal Dovetailer, or the UD (an Universal Turing Machine running all programs by using a scheduler/interlacer, starting with step 0 of program 0 at tick 0, step 1 of program 0 and step 0 of program 1 at tick 1 and so on). Marchal takes the assumption that the mind is computable (computationalism), and also makes use of Schmidhuber's UD, but unlike Schmidhuber which attaches consciousness to some specific body in some some computable universe's run, it asks the question of what subjective experience would such a simulated being have while being within the UD - the result turns out to be that assuming computationalism, you very easily end up with a Platonic view of reality where all the possible experiences (and apparent physical worlds) of a computable mind end up within the UD with some measure and nothing more or less has to be used to explain the entirety of physics (and most of mind) - an interesting side-effect is that you get something very much like the quantum indeterminacy in QM (explicitly as MWI) - and this is for all possible worlds within such an ontology - it comes with being the observer. I'll refer to this particular ontology as COMP from here on (computationalism with (subjective) mind, as opposed to eliminative materialism which is a computationalism with mind-as-self-delusion).
Aside from these 3 more radical views on ontology, I also ask you to consider the simplest possible (by Occam or by some formalized complexity measure) interpretation of Quantum Mechanics - it's the MWI(Many Worlds Interpretation).
Now given these possibilities for our reality, we have a few ways of attaining suh "unlimited" computational resources:
1) If COMP, you can easily run simulations including yourself which continue running "in the dust" or platonically (to be more correct) - as described in Permutation City (the simulation example in that particular book won't be stable within such an ontology, but there are ways of fixing this problem, but that's outside the scope of this response)
2) Regardless of theory (still computationalist though) -
http://en.wikipedia.org/wiki/Dyson's_eternal_intelligence
- not very practical, but might work.
3) If computationalism is false and we have concrete infinities in our mind's implementation or in physics - you have hypercomputation - unlimited computational resources right there (if you happen to be able to exploit them somehow).
4) If computationalism is true, a restatement of 1 - you are your mind's informational/computational pattern, if you can find yourself in any other structure, be it some Tegmark Level 4 Universe, somewhere in the UD, or a different MWI branch. I already explained the first 2 in example 1, so I'll explain the latter one here. Consider running a random program seeded from quantum noise (assuming MWI), you can have all programs up to some bound run in the different branches starting at some point (this is trivial to code, although for this to be of any use, you'd have to have enough resources to run enough programs).
Imagine you run this program, it crashes and you forget about it. You're now 100 years later a simulation. You die. You end up with a continuation 100 years ago in some branch. Repeat as many times as you want. (This obviously neglects that if COMP is true, you will have far more diverging continuations, but if COMP is ignored and only MWI is considered, this would work in a stable manner).
There's plenty of other tricks one can think of, but these are sufficient for now and some of them might scare someone quite a bit, after all, this view of computationalism implies a pretty heavy form of immortality, much more random than that of MWI quantum immortality. On the upside, you might at least get to compute/simulate anything you could ever want if you're lucky and you plan your things right.
References:
Tegmark:
http://arxiv.org/abs/gr-qc/9704009
http://arxiv.org/abs/0704.0646
http://arxiv.org/abs/physics/0510188
Schmidhuber:
http://arxiv.org/abs/quant-ph/0011122
Others:
http://arxiv.org/abs/0912.5434
http://www.hpcoders.com.au/nothing.html
Permutation City:
http://gregegan.customer.netspace.net.au/PERMUTATION/Permutation.html
Brain Marchal's COMP;
http://iridia.ulb.ac.be/~marchal/publications/SANE2004MARCHALAbstract.html
MWI tricks:
http://www.paul-almond.com/ManyWorldsAssistedMindUploading.htm
Worst case scenario in a single universe:
http://en.wikipedia.org/wiki/Dyson's_eternal_intelligence