Ok, so I have started tinkering woth hammer and have started making a map for PostNukeRP. Still a long way to go, but its getting there. Have a early version in the Downloads section of the RC site. Its early stages, so alot of work to do. I will be posting the more finalized version on http://garrysmod.org when I get to that point.
Also, there are a few others who are working on maps for the gamemode as well. So var there is a version of gm_disaster on the downloads section as well made by Carlover726.