MIDI Lab by Soundigy is a very powerful midi processor. If you work with plug-ins that respond to MIDI messages, you might want to look into it. I am glad I found this one. I had been running the demo version for a short time, and at first it was a standalone. I emailed the company and told them that it would be great if they would also make MIDI Lab available as a plug-in. Now it is available as a plugin for Windows and Mac. There are demo versions you can try out.
http://en.soundigy.com/midilab.php