MIDI Patchbay lets you hook up your various pieces of MIDI software and hardware and pass MIDI data between them, applying assorted filters on the way. Things like key splits, MIDI channel remapping, transposition, etc. are made very simple.
Version 1.0.3: It now has nice icons, thanks to Kevan Staples.
It runs native on Intel.
MIDI Patchbay and its source code are now under an MIT license.
ARVIDTP Handy little App I iuse all the time to patch MIDI in and out of apps that don't have their own virtual inputs. Just wish it had a function to save configurations. Also check out MIDIpipe if you like this. (Version 1.0)
ALEX REYNOLDS I use it for pulling together a bunch of MIDI hardware into one "virtual port" on different channels. It is indispensable (and free!). Great tool. Lacks the ability to save patchsets, though, but it is easy enough to set up. (Version 0.2)