Malevolent & Benign - You'd think I'd be really into a book full of shiny new 1st edition monsters, but this thing is just too wordy. Every time I go to read the fluff on one of these monsters I keep thinking Dave Hargrave of Arduin fame could've fit four times as many awesome critters in the same space. But if you like deep background info on your monsters, this may be right up your alley.
The Grinding Gear - Another absolute gem from Jim 'worst attitude in the OSR' Raggi. Like Death Frost Doom before it, this is a great item to drop onto your sandbox hexmap. Just leave it there, lurking menacingly, for some poor bastard PCs to stumble into. Things I wish I had thought of first: dead rats on the wandering monster charts. Like most of Raggi's best work, only get this one if you like material that demands that you DM outside your comfort zone.
X-plorers - I need another sci-fi RPG like I need a third bunghole, but I'll be darned if this doesn't look like a hoot. Remember how that old TSR chestnut Star Frontiers was basically Traveller for the Basic/Expert D&D kids? X-plorers is in the same conceptual territory, but I think it does a better job of it. If you like the mechanics of Swords & Wizardry look no further for your new favorite game about laser beams.
Adventure Games Publishing - The booklets that James Mishler has released recently are all sorts of awesome. I like Curses & More Curses and 100 Encounters & Treasures: Level 1. And Guide to the World of the Wilderlands is both a great campaign overview and a great format to rip off when writing an overview for your own setting. Monster Menaces Compendium 1-5 has the same wordiness of Malevolent & Benign above, but it also contains rules for the Chupacabra and the Rocktopus. It's hard to be dissatisfied with any book that brings that kind of radical-osity to the table.
Stonehell Dungeon: Down Night-Haunted Halls - One of the best things to come out of the old school hullabaloo. If dungeons are your bag, get a copy. Highest recommendation. 'Nuff said.