Just the unit, the stand, and the power supply.  Instructions can be found on linksys's website.

Linksys NSLU2 Network Storage Link for USB 2.0 Disk Drives addresses a key problem that occurs in most office LAN environments. As workgroup needs evolve for increased datastorage demands along with emergent technologies, increasing the storage capacity of your network becomes vital. With the availability of many accessory hard drives, it is possible to increase storage without overhauling your entire network and the NSLU2 makes it possible with greater ease than you might have imagined. Now you can quickly and easily add gigabytes of storage space onto your network with the Network Storage Link from Linksys. This tiny network appliance connects USB 2.0 hard drives directly to your Ethernet network. You can connect up to two stand-alone USB disk drives of any size, and access them from anywhere on your network. You can even plug a USB flash disk into the Network Storage Link, for a convenient way of accessing your portable data files. The Network Storage Link can also be set up so that your storage devices are accessible from the Internet -- files can be easily downloaded via your web browser. Your files can be available publicly, or create password-protected accounts for authorized users. Installation of the Network Storage Link is simple -- just plug it directly into your 10/100 Ethernet network, and attach your USB 2.0 hard drives or flash disk. It can self-configure to your network via DHCP or you can use the built-in utility to manually configure it. With the speedy USB 2.0 interface, you'll get quick response times with even your largest files.