x86_64 な CentOS 5.5
rpm -ivh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
rpm -ivh http://rpms.famillecollet.com/enterprise/5/remi/x86_64/remi-release-5-8.el5.remi.noarch.rpm
yum --enablerepo=remi,epel install memcached