The whole of the WWW has been likened to a flea market. Lots of good stuff scattered around in haphazard fashion. One way would be to use a directory much like the telephone yellow pages. Such directories exist, but by the time they are printed, they are out of date. The preferred way, therefore, is to use the web itself and find information by electronic means.
Search engines provide the means.
As you might imagine, these lists quickly became quite large. You can still find index sites where you start with high-level topics and drill down through listings that are progressively more detailed. You are then presented with a list of these sites with links for instant jumps to sites of interest. It depends on the engine. Some rely on inputs from web creators who submit requests.