RPMForge is a special repository for rpm based Linux which contains various software and packages for Linux desktop or Server. The RPMForge now move its website to RepoForge. You may visit their website here. Here we provide the download link for rpmforge-release for CentOS 7, RHEL 7 and all derivatives.
rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm
To install use the command
rpm -ivh package-name.rpm