I've been an XSI User for years and, even if Blender is really a great program, I was really missing the keyboard configuration. This is why I created an XSI keyboard configuration for Blender. I thought you might whant to include it with the Maya and the 3DS max preset already avalible in Blender.
I don't think it is really an add on, but I sent an E-mail and Ton Roosendaal told me to post it here. If there is any bugs in it I accept to correct them, but I don't see how bugs could happens in a shortcut presets throught.
Anyway, I would really appreciate to see this preset in a futur version of Blender. It would be very usefull to me.