If you're willing to script yourself, HKN is free.
AHK (Auto Hot Key) is your alternative, for scripting.

IS Boxer has a GUI, and Lax gives amazing support.
I don't know of anything that compares to what it can do.

If you're shopping around...
Keyclone is $20 once, for a lifetime license... but it's not as advanced as HKN/ISBoxer.
Game Commander Pro, haven't heard from them in a while, but their product looked good a few years back.
Pwnboxer is out there too, but it costs more than IS Boxer and isn't as powerful.