VTT allowed my friends and I to keep gaming during covid with all of our lockdowns.
Drivethru has allowed me to access a number of RPG products I likely wouldn't have seen down here in NZ and because I'm purshasing a pdf more often than not, I have instant access. I have also built up a large repository of DnD Basic, 2e, and some 3e products from DMsGuild.
Reddit and other online communities have a lot of creative content by RPG players, new spells, new subclasses, new classes; you might not use it all but just browsing through it you might come across something and go "yeah, I think that fits my next adventure I'm running"
Discord has allowed me to ask queries about Dolmenwood and Transformers RPGs and, because the community for both is very active, I get a response almost instantly. Forums and Reddit might take a bit longer, but not by much, these communities have been a great help in clarifying information or helping me sort out an idea.
Kickstarter has been great for the limited projects I've backed. People have mentioned Humble Bundle and Bundle of Holding, I check these every couple of months and have ended up with large collections of stuff from them.
DnDBeyond has made 5e character creation nice and easy, I loved it back when I was playing 5e and had a bit of fun creating monsters and magical items for encounters and players.