help with/looking for/implementing audio fx externals for dj system

I'm building a dj system and am looking for some CPU friendly stereo audio FX externals to to be used as send effects. They can be reverb, delay, combing, or any interesting form of mangling :) This is part of my dissertation for uni which is based on open-source/community Vs high price manufacturers and I would really, appreciate even the most basic patches :) It could be something that you've created yourself or something that you have adapted (if you do then could you please mention the origin of the patch, please?).

As part of the open-source/community/GNU licence spirit I would like to allow the community some means of creating plug-ins for the system. This project is only a prototype at the moment and is being built in conjunction with a unique hardware device. I envisage that the send FX will have 2 dials and 2 buttons assigned to them on the hardware device as a means to control the functions, though further functions can be controlled on-screen. I would appreciate some advice on what I would need to do to set-up my patch to allow

All work is fully credited/referenced to those submitting any work, advice, ideas, comments - it's actually in my best interest to do this. If anyone who is going to submit something and would like a copy of the DJ patch, then let me know :)