Use RPMforge repository for extra 5000 packages for CentOS 6.
Full list of packages : http://packages.sw.be/
Here is Howto.
1. Download *.RPM
[root@nTOP ntp]# wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm <— 64bit
2. Install DAG’s GPG key
[root@nTOP ntp]# rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
3. Verify the package
[root@nTOP ntp]# rpm -K rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
4. Install the package
[root@nTOP ntp]# rpm -i rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
5. Testing
[root@nTOP ntp]# yum install htop