Distributions like CentOS are more enterprise orientated, so don't expect to end up on the most recent kernel. CentOS is essentially a recompiled Red Hat Enterprise Linux, and RHEL sticks with a known-good kernel for quite a while. They do, however, back-port security fixes into their kernel as necessary.
"I quasi-regularly update my kernel at home, with CentOS repositories. The latest available kernel is 2.6.18-164.11.1.el5.centos.plus as of this writing for CentOS.
If you want to get 2.6.32, then you'll have to compile from source, as other posters have mentioned."
