If the command yum search lame returns no results – but you do need lame for making sure, that mp3 files can be created – please follow this quick howto.
Lame as well as many other packages are not by default available in CentOS/RHEL repos. You have to either compile them yourself or use http://repoforge.org/. The latter option is much easier and I would also say – much safer.
To make it quick you have to download the appropriate rpmforge-release package that fits your distribution. I have been installing it on CentOS 6.4 – that means EL6 (to find it out just check contents of the /etc/redhat-release file).
On that particular server I am running a 64bit version, hence:
wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm rpm -ivh rpmforge-release-0.5.3-1.el6.rf.x86_64.rpm
…and you are pretty much up and running. You can now install lame as well as other packages provided by rpmforge.
yum search lame [ cut for clarity ] lame.x86_64 : LAME Ain't an MP3 Encoder... but it's the best of all lame-devel.x86_64 : Header files, libraries and development documentation for lame. twolame-devel.x86_64 : Development files for TwoLAME toolame.x86_64 : MPEG Audio Layer II VBR encoder twolame.x86_64 : Optimised MPEG Audio Layer 2 (MP2) encoder