First of all, let me respond to the ReiserFS naysayers:
a) ReiserFS3 is a stable, fast, space-efficient (specially with lots of small files), reasonably maintained (just check the kernel changelogs) and extremely robust filesystem: I've used ReiserFS in all my servers (a few dozen of them) since 2001 or so and it has never given me any trouble. In fact, in a client of mine with constant electrical power interruptions, they repeatedly had to restore EXT4-based machines from backups because the entire filesystem was frequently hosed beyond fsck repair, but the CentOS servers we configured for them almost 4 years ago (using ReiserFS3 of course) have never ever lost any data (and just keep on going to this day). I've noticed reader-writer-consistency problems with some of the more modern kernels (2.6.37 comes to mind), but with all stable 2.6.x kernels up to and including 2.6.32, ReiserFS3 runs solidly as a rock.
b) Of course what Hans Reiser did is wrong, and I for one am glad he's in prison paying for his crime. But an idea isn't responsible for the acts of its creator... Or would anyone seriously propose that Hans Reiser's murder of his wife is in any way connected with the ReiserFS filesystem?
c) The OP requested a solution to run ReiserFS on his CentOS server, not a lecture on the merits of other filesystems and/or the demerits of Mr. Hans Reiser, so I think we would all do a lot better if we just stick to the matter at hand.
That said, here's the solution the OP asked for:
1) Add the ElRepo repository to your YUM configuration: just follow the directions at the "Get Started" section of the ElRepo site.
2) Run "yum update" to pull in repo metadata about the available packages;
3) Run "yum install kmod-reiserfs reiserfs-utils"; that way you will install both the kernel module and the needed userland utility programs (mount, mkfs, fsck, etc).