The Stardew Valley multiplayer beta allows you to invite up to three players to your farm over the internet or a LAN connection. Since they need a place to live, you also need to build them three cabins. But what if you want, say, a hundred friends to join you in Stardew Valley for some farming royale?
The answer is: mods. The Unlimited Players mod for the Stardew Valley multiplayer beta uncaps the limit on friends and cabins, so invite as many pals as you want. Keep in mind, if you want scores of friends on your farm you'll still need to build each of them a cabin, at least for now. The mod, which is a work in progress, may lift the one-cabin-per-day build limit or remove the requirement for cabins altogether in the future.
I also imagine the game might not run so well with a hundred farmers hustling around, but it sounds like it'd be fun to try it. Visit the mod's page on Nexus Mods for download and installation instructions.