PeterS wrote:I wondered if anyone had used an Arduino to connect a USB keyboard/mouse to a computer with ps/2 sockets.
Not to my knowledge, but sure it can be done. You would need a USB host shield, or an "Arduino" of some kind that has USB host capabilities, because it would be tricky to bitbang both PS/2 (two ports) and USB host reliably at the same time.
PeterS wrote:This would open up a great many USB keyboards for use with the Milan.
The appropriate solution is of course to use an IKBD->PS2 adapter so you can use a TT/Mega keyboard with your Milan
I did that six or seven years ago.