ToDo

EL5 Packages
Realtek r8187B (see ML request. Implausible, see follow-up here.)
rt61pci backport from upstream kernel (see ELRepo bug tracker) — kernel-2.6.24 appears to be the first mainline kernel containing the driver
powernow-k8: Update to the code in the -164 -194 kernel (minor change)
VirtualBox (kmod-vbox)
VMware (kmod-openvm)
OpenAFS (kmod-openafs)
GPFS (kmod-gpfs)

Miscellaneous
kmodtool improvements
weak-modules bugfixing
collaborative work with Jon Masters (see Red Hat bug tracker (external link) and ELRepo bug tracker )
generic document: How to Build a Kernel Independent, kABI Tracking, Kmod Package for Enterprise Linux 5.

For the Future
btrfs (external link) Once EL6 is released. (btrfs is not viable with EL5.)