As far as Speedway stuff goes, majority of the tracks and the NZ Superstocks mod is over at NZDR now (
http://nzdr.boards.net/)
Other mods like NZ Streetstocks, Midgets, Sprintcars etc were all hosted recently at SRNZ but SRNZ has closed its doors start of this year, I personally have the streetstocks as I made the mod, but unsure who else hosts the other mods.
The stuff Kokpit has made is a closed community - you have to know someone to be "Invited" in, and then they have a membership fee and very strict rules that you have to adhere to in order to remain a member. Its a bit of an "Gentlemans Club" so to speak over there. They have their own self created mods that they haven't made available to the public.