If like me your running debianslug on an NSLU2 and you'd like to mount an iso file so it can be directly streamed to Xbox Media Centre (its a beautiful solution isnt it!) then simply do the following.
Ensure you have loop support in your debianslug kernel. This requires your running debianslug 3.10 bin
NSUL2:~# uname -a
Linux NSUL2 2.6.16 #1 PREEMPT Thu Jun 8 23:38:13 PDT 2006 armv5tel GNU/Linux
Get the ipk file for loop
Install the ipk file (dont worry about any reported errors)
NSUL2:~# dpkg -i --force-architecture kernel-module-loop*.ipk
NSUL2:~# depmod -a; modprobe -v loop
Now mount your .iso file
NSUL2:~# mount -o loop -t iso9660 /path/to/iso /mnt/mountpoint
ps thanks to Int16h and EvilDevil on the #nslu2-general channel for answering a few questions on this subject!