Someone posted it on the SA forums and i thought it might intrigue you guys (and didn't show up in a search). Basically it's CTF where you have build (the fort) and fight stages. You use the grav gun to "build" your fort and then fight out a traditional CTF style game. Now I could see this blowing on a lot of Pub servers but Ausgamers is normally a bit classier. Any love?

http://www.sourcefortsmod.com/

Apparently garry's mod (for source) has a version of source forts that is better. Dont know for sure though cause I havent played.