Is there an AutoHotKey for Ubuntu?

The links in nik's answer are a bit old but still pretty useful, although there have been quite a few advancements since then. There is IronAHK currently available which is a complete rewrite of AutoHotkey which works under .NET as well as Mono, allowing it to have cross-platform compatibility. It's also free and fully open source.

"Landed here earlier while searching for one myself.

There is now a opensource & cross platform alternative.
Robotjs handles mouse, keyboard, and screen(pixels) inputs with js code.

http://robotjs.io/

Example from the website:

// Type ""Hello World"" then press enter.
var robot = require(""robotjs"");

// Type ""Hello World"".
robot.typeString(""Hello World"");

// Press enter.
robot.keyTap(""enter"");"