I've been providing a rebuild of the excellent Elrepo kmod drivers. These newer drivers are back ported from upstream so that they are compatible with the EL5 kernel, and provide support for newer NIC's that aren't available.
You can find them here:-
ftp://timburgess.net/elrepo-kmod
If you already have my repo setup, you can install using Yum
yum --enablerepo=timb install kmod-e1000e