Since processing version 2.0, there is the possiblity of running processing scripts from the command line. That is not super convenient in itself, but coupled with a decent programmers editor such as vim (that I'm using here), emacs, textmate or jEdit you can run scripts without the need to move away from the editor.
Get jEdit here, you can download some of jEdit tools at the jEdit community website.
Get processing here
alternative language support
I've also produced tools for working with processing.py
jEdit for JRubyArt and ruby-processing
Extract zip in home folder ("My Documents" windows), creates
.jedit folder (or extract into
.jedit folder if exists) macros need to be tuned for OS java version see jEdit for details.
For JRubyArt prior to version 1.2.0+ use k9.xml in this folder to replace the current commando file.