On a Red World Alone - A REALLY weird and darkly hilarious campaign set on Mars after a disaster wipes out Earth and the remnants of society have turned into a nightmarish mashup of primitive barbarism and cyberpunk. Come for the great city-based setting and retro-future aesthetic, stay for the horrifying sex and magnificent NPCs.
Dungeon Moon - This idea is so good, I'm thinking about stealing it for a Holmes Basic campaign. The play reports are as awesome as the setting, and I wish there were more of them. I love the quiet desperation of the town, and how it's juxtaposed with the world of fallen luxury and magical degeneracy below. Also includes an atheist paladin (a fighter), which is just delightful.
World of the Lost: Die Verboten Schatzgrube - If this doesn't convince you to buy World of the Lost, nothing will. But don't get me wrong: the DM and players bring so much creativity and originality to this campaign that the play reports always leave me amazed and kind of jealous. Manages to be horrifying and fucked up even with characters that come across as competent and powerful. Plenty of fantastic NPCs and social bits, too. Not to mention some truly odd and unpredictable magic scattered all over the place. This one might actually be my favorite, but these are all so great that it's hard to decide.
Fallen World Campaign (a.k.a. the Lamplighters campaign) - The DM has done an incredible job linking a whole bunch of different LotFP and OSR supplements together into a cohesive whole. Interesting stuff is constantly happening here, and the players have a great sense of humor about everything. Bonus points for using Carcosa in a unique and fascinating way, and for including a monologue from an NPC that doesn't suck.
Tales of Greed - Here's one from the official LotFP forum, and it really needs more love. It's actually really funny and action-packed, with a ton of cool moments happening due to player ingenuity and/or foolishness. This is a great example of what an awesome 1600s European LotFP campaign could look like. Bonus points for allowing demihuman players in LotFP and still managing to not suck.