AutoHotkey is a basic scripting/programming language used to automate tasks on your Windows PC. This may sound intimidating to the average user, but it is probably the easiest scripting/programming languages to learn. On a very basic level, you can designate hotkeys to preform actions when that hotkey is pressed, but that just skims the tip of the iceberg. AutoHotkey can be used to send keystrokes, send clicks, hide and unhide windows, show message boxes and more. Just use your imagination and you can do anything that involves any of those functions. Here are a few particularly innovative applications of AutoHotkey:

Remap Capslock to Minimize

Turn that annoying Caps Lock key into a useful minimize key. This is a versatile hack because it isn’t limited to just a minimize key, the possibilities are virtually endless.

A drop down Quake-like Console

Have a permanent console running with the dropdown quake style. I use this daily

AutoHotkey Resources:

Official Documentation
The official documentation from autohotkey.com

Lifehacker Tutorial
The folks at Lifehacker did a nice job putting together this tutorial

AutoHotkey Download Page