If you were looking for the latest edition of Weekend Download, I'm sorry to inform you it's been in a terrible accident involving scissors, a blowtorch, and those annoying little pudding cups in the aluminum tins that, if you snap off the "easy open" tab, suddenly become an impenetrable fortress of pudding protection.
NUD (Windows, 1.5MB, free) - A tower defense game that puts heavy emphasis on the placement of towers (called NUDs) in relation to each other. NUDs provide adjacent NUDs with various bonuses, so if you want to maximize your firepower, experiment and come up with the best tower arrangement. A forgiving build/undo system lets you tweak and refine your pattern with ease, and a sweet old-school vector graphical style does nothing but add to the game's appeal.
MacHeist 3 (Mac/Win/Linux, free) - In MacHeist 3 you take on secret agent-style missions by solving Flash-based puzzles right in your browser window. Dig deep enough into the espionage story and complete the puzzles and you'll score a collection of free Mac-only software (while helping out charity organizations as well). Any operating system can play the games, but only Mac users can enjoy the booty. You have to register to play, but it only takes a second, and you'll appreciate the nice prizes for playing a few simple browser games.
Afterlife: Rickard's Quest - (Windows, 4.5MB, free) - An extra-challenging action/puzzle game that relies on physics and precision movement to lay on the difficulty. You control a hot air balloon (piloted by Rickard, of course) and can toss bombs and use a Deadly Hunting Umbrella to vanquish foes. There are tons of unlockables, including extra game features, new balloons, and unique abilities, all spread out over 100 levels. Certainly more than an afternoon time waster, and you can't beat the price!