Here are a couple of mindless Flash games for those times when you just need a diversion. First up: Lunar Command. You shoot down incoming missiles to protect your lunar base. Hmmmm. I wonder why they don't call it Missile Defense?
Here's one in which you shoot bubbles at bubbles. It's more fun than it sounds. It's Bubble Trouble.
Both of those games, and many many more, can be found at AddictingGames.com.