Social media, although we do still have taverns. Coffee houses, too.
Taverns are places where people can meet "under the radar," so to speak, to discuss issues both public and private. Under a repressive regime, any gathering of three or more people in a private place is a red flag for some kind of insurrection-bound behavior. But taverns have always been places where people grouped informally, and meetings at such places went unnoticed. After all, why wouldn't five or ten or fifteen men be in a tavern at the same time?
Of course, alcohol flows freely at taverns, which results in any meeting of minds losing its focus after an hour or two. The French Revolution was hatched by men in coffee shops to prevent this outcome, and cafés became popular meeting places as well.
When the "three martini lunch" was banned in some quarters back in the 1970s (Businessmen would get very drunk together and claim the meetings as business meetings, and therefore deductible for tax purposes), coffee houses became even more popular. This coincided with the sudden growth and nationwide expansion of Starbuck's and similar enterprises.
Today, many of the discussions that occurred in taverns and coffeehouses--of a business or political nature--occur online, in chat rooms and on private Facebook pages.