Back in the heyday of forum-based RPs, organizing a game night was easy: you’d just pop a “BGO, anybody?” in the chat and off you went. These days, spontaneous fun is rare - apart from the play-by-post forum games, that is.
Some webgames, off the top of my head, include:
Cards Against Humanity (http://pretendyoure.xyz/zy/)
Town of Salem (http://www.blankmediagames.com/TownOfSalem/)
Would there be interest in organizing a game night?