The main ones I use are Music For Life, Leo Finance and STEM. I am about to post on the Cine one. I may not always use the dedicated sites as I tend to post from peakd or ecency.
It's good to have all these options, but I think we need a uniting brand so people know there are others. There could be a 'Built on Hive' logo, but of course Hive is a hard thing to search for. Branding does matter and I think we have been lacking in brand awareness.