Dead before dawn on that link looks like it might be quite good.
I might download it tomorrow and test it. :?
"This campaign is not yet released and is still in production.
Once released you will be able to instantly download the campaign, Dead before Dawn."
Looks like it'll be a while before it's out.
Looks like it'll be a while before many good custom maps appear tbh - there's a lot of work in producing a full campaigns worth of maps. The only reason dead before dawn is getting there is because it had a head start - it had been in development quite a while before L4D came out - originally for some half life 2 mod.