Is there a list / archive of hbc forwarders? I know I can search for forwarders on the internet but It would be more practical if there was a big thread with all the available hbc forwarders.
You can build a forward dol (or ISO) for any path, website, or title ID using ModMii Classic's advanced downloads page. You can take these dols and inject them in a wad or load them via priiloader, or whatever. You won't find an exhaustive list of all the forwarders in any one place because any one can create a forwarder and save it in some remote corner on the net.
The best I can do to help is share my channels. At the bottom of my post I shared links to some other threads with some amazing channels. This is probably the closest you're going to get especially because some people might not appreciate it if you mirror or repost their work (personally I'm fine with it as long as you share credit).