XBMP is dead and buried, anything XBMP could do XBMC can do better
It can play most quicktime files, has a builtin file manager that can read pc CD/DVD's, etc
Personally, I prefer the way XBMP works which is why I still use it. For files it doesn't play I use XBMC. In a way it's analgous to the Amiga - just because it has been discontinued it doesn't make it any the less useful.
The cheap way of connecting a keyboard or mouse to the xbox is quite simply to cut off the usb connector of a keyboard or mouse and cut off the plug and cable of an old xbox controller. Then just twist each bare wire on the mouse keyboard with it's corresponding wire from the xbox connector and cover them in insulating tape. Job done.
Xbox cable > Usb Cable
+5v = Red > Red
Data - = White > Yellow
Data + = Green > Orange
Ground = Black > Black
There should be an tutorial on www.xbox-scene.org