Gamers Plane is a fantastic site that hosts a large variety of play-by-post role-playing games.
Norse Foundry makes fabulous dice, coins and other RPG accessories that DMs and players will love.
Godsfall is a high quality actual-play RPG podcast set in a custom 5E setting.
She’s a Super Geek is an amazing actual-play RPG podcast highlighting women as DMs.
Roll20 is an online virtual tabletop that our group uses to play RPGs.
DriveThruRPG is a huge online store for downloadable RPG content.