Gold said: The Master's Vault is a relatively small module, with premade characters which helps with a one-shot. Lost Mines of Phandelver is also not extremely long adventure, but is typically more than a one-shot worth of adventuring. The "Double Dungeons" module products are mostly made as one-or-two shots, and you get 2 of those in each double-dungeons purchase. Add-ons are not necessarily mini-campaigns, but some can be played that way. The newest set of add-ons, Tales From The Yawning Portal, consists of several classic adventures, in which the first one at lowest level (The Sunless Citadel) would be a good starter-adventure and potentially a one-shot. +1 for most of these suggestions. However, LMoP should not be suggested in the same thread as one-shots unless you're just picking certain dungeons to run through. LMoP is a pretty extensive starter campaign intended to get players from level 1 to 5. Fastest I've ever heard of it being completed is 11 hours of play with players already at level 5 and focusing on purely main story without doing side quests. Most groups usually get at least 36-40 hours of play out of the module, if not more.