Swords & Wizardry my review of Revised - OD&D rather than B/X which is very cartoony. Much more, uh, complete than White Box, much simpler than AD&D, really a great sweet spot.
Advanced Fighting Fantasy, Troika!, etc. - great simple game, minimalist rules, setting-as-system in Troika's case.
Monsters! Monsters! is replacing Tunnels & Trolls, which has been bought & sold a couple times now and is in limbo. M!M! runs all the T&T adventures, esp. the solos, and is a great pick-up game.
I love the adventures for Lamentations of the Flame Princess, but the system's been neglected, the Referee book is still not out, there's no monster book, etc. But the adventures work in any OSR game with minor tweaking.