AutoHotkey

Introduction
AutoHotkey is a free, open-source utility for Windows. With it, you can:
* Automate almost anything by sending keystrokes and mouse clicks. You can write a mouse or keyboard macro by hand or use the macro recorder.
* Create hotkeys for keyboard, joystick, and mouse. Virtually any key, button, or combination can become a hotkey.
* Expand abbreviations as you type them. For example, typing "btw" can automatically produce "by the way".
* Create custom data entry forms, user interfaces, and menu bars. See GUI for details.
* Remap keys and buttons on your keyboard, joystick, and mouse.
* Run existing AutoIt v2 scripts and enhance them with new capabilities.
* Convert any script into an EXE file that can be run on computers that don't have AutoHotkey installed.


I was searching for one of these for quite sometime. Written in C++ this is a very beautiful and small application - completely open source has been released under the GNU license. I am awe struck cause it gives me complete freedom to configure and create and run my own macros - keyboard, mouse, joystick...
It might look a bit difficult in the initial go but once you see a few examples and try out some simple scripts it will be a breeze through. I wonder why I never found this before! This definitely fills one of the major gaps in my open source collection. Some of the scripts I am using are:

#z::Run www.google.com
::btw::by the way
:*:. ~::. ~dacscan/.profile;TERM=vt100{Enter}
:*:Than::Thanks,{Enter}-MyName;-)
Numpad0 & Numpad1::Run Notepad
Numpad0 & Numpad2::Run Calc
LAlt & WheelDown::AltTab
LAlt & WheelUp::ShiftAltTab
AutoHotkey was mentioned at the Lifehacker blog in its download of the day section.