Just discovered this today, it’s free:
http://sonicbirth.sourceforge.net/
Don’t let the description fool you, it also exports VST. I had a go at it earlier, read the documentation and made a basic effect. I have to say it’s a pretty good tool. Unfortunately, OS X only. No multi-platform plugins. The knife cuts both ways you windows users with all your plug-ins! 
Unfortunately, I have no idea what I’m doing when it comes to this stuff, but the fact that I was able to get something working is a miracle in itself. It was quite easy after reading the documentation.
I imagine a more intelligent OS X user will have better luck at this. Maybe someone can clone dblue glitch? 