I recently bought a VPS to host a Counter Strike server. WIthout having any choice, I was stuck with CentOS 5. After getting everything set up, I wasn't left with much disk space left. So, I read the man page for sort and used the following RPM command to find the largest packages installed:

rpm -qa --queryformat '%{name} %{size}\n' | sort -k2n

The option -k2 sorts the second column (size) and the -n option sorts it numerically. I also found out that sort -h doesn't work under CentOS 5 since it has coreutils 5.97, as it requires coreutils >= 7.5.