Mac: Switching between apps on a Mac is usually as simple as Command+Tab, but if you want switch between specific windows it's a little trickier. Contexts is an app that makes it easy to swap between large numbers of windows right from your keyboard.
Contexts offers a few different ways to cycle between windows, including two different keystrokes, a search menu, or a mouse interface. When you trigger Contexts, it pops up on your screen and you can quickly load up the specific window (or app) you want using just your keyboard. It's similar to Witch, but it's (currently) cheaper. You can check out Contexts for free right now while it's in beta or buy a licence for $US7.