USB

[edit] General Information

The Xbox 360 comes with 3 standard USB 2.0 ports. (2 on the front and 1 on the back)

Can be used to add hard disk and get around DRM. SEE: http://llamma.com/xbox360/mods/USB Hard Drive Mod.htm

iPod and standard USB flashdrives using the FAT(32)? Filesystem are detected via the 360 media center.(Cannot read NTFS)
The Xbox 360 seems to be able to read the HFS filesystem Mac formatted iPods.
It is unknown if the USB ports can access DMA but it is speculated that the USB ports may be read-only. Such speculation is questionable, as two-way communication is required to be able to communicate with products. Instead, any read-only access control may be implemented in the Dashboard, or write support may simply not exist within the filesystem drivers. - This is most likely impossible - There are no "slave initiated DMA" transactions as part of the USB spec. Even if it does support USB OTG, and therefore can act as a Slave, a driver [on the xbox] would still need to be present for any usb endpoints to exist.