What makes now special? I recently came across the paper Relation between the psychological and thermodynamic arrows of time (arXiv).
Their argument makes sense to me, however their concept doesn't seem to address what 'now' is.
If each person exists in an unchanging state in the block universe, and the flow of time is an illusion caused by the way memory functions, then how exactly does this illusory sensation of 'now' work? Are there an infinite number of me's at every point in time, all experiencing their own now? Or is there one me that 'travels' though the block universe, experiencing the illusion of time? And what is it that is experiencing this illusion of movement?
 A: Even if there is no agreement in the physics community about what is special about "NOW", I believe that most physicists that believe in a block universe would agree with your statement that there are an infinite number of me's at every point in time, all experiencing their own now.
Not only that, there is an infinite number of mathematical universes (see Max Tegmark's work) in which different "you"s experience different alternative realities. The issue of when the "you" becomes someone else (that is, when he is different enough to be considered an entirely different person) is a matter of debate in philosophy too (I'll try to find references to the articles that deal with these issues).
A: In note [5] of your paper, check the recent paper The physics of 'now', James B. Hartle. Hartle builds models of simple information gathering and utilizing systems and explains how past, future and now may be concepts describing IGUSes process information. It is interesting to point out different IGUSes can have drastically different and bizzar notions of "now" as we conventionally understand. All are consistent with 4 dimentional fundamental physics. So the notion of now as we understand is not really a necessary consequence of fundamental physics but are the results of laws of physics and particular mechanism of the human IGUS, according to Hartle. 
In note [4], In Memory Systems, Computation, and the Second Law of Thermodynamics, Wolpert distinguishes between two kinds of memories, one that remembers past and future and one that remembers past only (like the human brain). Wolpert's argument makes more sense to me than your paper. Maybe you want to check it out.
A: To address the issue of "...then how exactly does this illusory sensation of 'now' work", let's consider the mathematical multiverse mentioned in Julian Fernandez' answer above. If you take this seriously, then you should consider yourself to be a mathematical algorithm. A mathematical algorithm can be defined by consdering how it acts on certain states, but it cannot be construed as being such a state that it is acting on. Restricting ourselves to a universe described by quantum mechancis, this means that it is wrong to associate an observer to a wavefunction (or density matrix), rather one should describe an observer by an effective Hamiltonian. Obviously, this implies that the flow of time is encoded in the description of the observer as he exists at any moment (the Hamiltonian is the generator of time translations).
The formalism developed in this article fits in well with this idea, although the authors use it to address different issues.
