This seems to be a repetitive topic. Thought I share my latest findings with you.
MidiYoke is the most known one I guess, but not 64bit compatible
http://www.midiox.com/index.htm?http....com/myoke.htm
Marple is probably less known but recommended by some developers, also just 32bit
http://www.maplemidi.com/Maple_driver.html
LoopBe by
Nerds, 64bit compatible
LoopBe1 is free - but just one cable
http://nerds.de/en/loopbe1.html
LoopBe30 is $19.99/16.99€ and offers 30 cables
http://nerds.de/en/loopbe30.html
ipMidi is 79/69€ and offers midi over UDP networking
http://nerds.de/en/ipmidi.html
rtpMidi is
free and
64bit! Works on one pc or over
networks too!! Is
Mac compatible, i.e. connects to Mac midi networks!!! Needs Apple Bonjour network services which can be downloaded for free from apple
http://www.tobias-erichsen.de/rtpMIDI.html
http://www.apple.com/de/support/bonjour/
This is HOT and around for approximately one month - the most versatile you can get for free (or any donation you wish to contribute to the developer)
Have fun cabling midi!