1) MIDI OX http://www.midiox.com/ it can monitor, merge, filter do all sort of weird stuff with your midi devices, very helpful if ypu have little hardware ports and a lot of applications wanting to use them (Windows)
2) MIDI YOKE http://www.midiox.com/myoke.htm virtual MIDI ports, along with MIDI OX create a pairt of must have tools, with those two programs you can do anything midi wise (Windows)
3) Xmon, (win http://ctrlr.googlecode.com/files/Xmon_Win32.7z osx http://ctrlr.googlecode.com/files/Xmon_Mac_UB.dmg) my little utility let’s you see what’s happening on the MIDI wire in terms of bits bytes messages, it understands NRPN and RPN messages it can dump a message bit by bit, you can send custom messages and catch responses (Windows, OSX)
4) MIDI Yoke for OSX exists in OSX itself, just go to Utilities->Audio And MIDI Settings, and look for the IAC driver, add as many wirtual devices as you want, you can use them with Xmon lto see what’s going on.