This doesn't really have much to do with modding itself, but would it be possible on the main site to group all of the files that are in OMOD format together? Or if there is a list that already exists could someone please point me in the right direction?

Any mod can easily be made into an OMOD.
However, If you would like to go through the 12,000 or so mods on the site and flag each one, then we would be able to sort for OMODS.
A good idea, but not really practical right now.