Examples of hyperstonean space From the abelian von Neumann algebra, I see the hyperstonean space as its spectrum（analogy with the C*-algebra). Now I want to see some examples of hyperstonean space.
1) Can you give me a hyperstonean space which is not a stonean space?
2) Does a Cantor set be a hyperstonean space? If not, can you show me some concrete hyperstonean space?
 A: The second statement in Martin's answer is not quite correct - the Cantor space is totally disconnected/zero dimensional but NOT extremally disconnected/stonean.  To see this, let us first be clear about our representation of the Cantor space $C$ as, say, real numbers in the interval $[0,1]$ that have ternary expansions without $1$'s.  Take a point $x\in C$ which has infinitely many $0$'s and infinitely many $2$'s in its ternary expansion.  Then the points below $x$ in $C$ and those above $x$ in $C$ will both be open and have $x$ in their closures, i.e. the closure of either of these open sets is not open and hence $C$ is not stonean.
The first example of a stonean space that is not hyperstonean was given indirectly by Dixmier.  He gave an example of a commutative AW*-algebra $A$ that is not a von Neumann algebra which, as Martin alluded to, means the spectrum/pure states of $A$ are stonean but not hyperstonean (when given the weak* topology induced by $A$).  I have never been able to track down the original paper but I have heard that his example goes something like this.
Consider the C*-algebra $B$ of all bounded Borel functions from $\mathbb{R}$ to $\mathbb{C}$.  The $f\in B$ with meagre (i.e. countable union of nowhere dense sets) support $\mathbb{R}\setminus f^{-1}\{0\}$ form a closed ideal $I$, so $A=B/I$ is a C*-algebra.  Every Borel subset $S$ of $\mathbb{R}$ is, modulo a meagre subset, the same as a unique regular open subset $RO(S)$.  So projections in $A$ correspond to regular open subsets of $\mathbb{R}$, which form a complete lattice.  Thus $A$ is an AW*-algebra.
However, $A$ is not a von Neumann algebra, and does not even have any non-zero normal positive functionals.  To see this note that, as the $RO$ function preserves countable supremums, any normal positive functional on $A$ would induce a (positive countably additive) Borel measure $\mu$ on $\mathbb{R}$ which is zero on all meagre subsets.  For each $q\in\mathbb{Q}$ (or any other countable dense subset of $\mathbb{R}$), $\mu(\{q\})=0$ so we can take an open interval $O_q$ containing $q$ such that $\mu(O_q)$ is as small as we like.  In particular, if $\mu\neq0$ then we can make the intervals $O_q$ small enough so that $\mu(C)\neq0$, where $C=\mathbb{R}\setminus\bigcup_{q\in\mathbb{Q}}O_q$.  But $C$ is meagre (even nowhere dense) by construction, so we have a contradiction.
And lastly, if you want an explicit example of a hyperstonean space then you can simply take any set $X$ with the discrete topology (arbitrary subsets are open), or its Stone-Čech compactification $\beta X$.
A: Every hyperstonean space is stonean. This corresponds to the fact that every von Neumann algebra is an AW$^*$-algebra. 
The Cantor set is stonean, but not hyperstonean. I have read  this assertion by experts, but I don't know the proof. 
I don't think there are any "explicit" examples of hyperstonean spaces. Hyperstonean spaces are the compact sets such that $C(X)$ is a von Neumann algebra, and that's likely their best characterization. 
