Mischievous Monsters - This is a curious adventure because it weights in at a 130 megabytes for 30 pages. Even the preview is 130 megabytes. $3.90 and no levels or specific game listed.
Night of the Mad Kobold - Already mentioned it, free 20 pages adventure
Outer Space Raiders: Zeloxians - I'm sure eventually Zelox will be the name of a drug. New alien races, 99 cents, 4 pages.
The Vagrant - A free class from Shane Ward of 3 Toadstools. Sort of a down on his luck thief. 7 pages.
OSR Sci-Fi Screen - For White Star, but claims to be compatible with other OSR sci-fi games (Hulks & Horrors and Stars Without Number are cited, and there are several more), but most of them actually have rather different rules so I'm not sure how compatible they would be with it. $4.99 and 8 pages.
Over the Top: Character Primer - A supplement for Labyrinth Lord which isn't about playing arm wrestling truckers but something even more intriguing, fantasy characters on a WW1 style battlefield. Neat concept, little pricey at $3.69 and 17 pages.
The Sandbox #2 - Free e-zine from Sine Nomine features a new class and lifepath generation for SWN. 21 pages.