D-Link's DSM-G600 gives you the option to make your network storage wireless. It supports 802.11b/g and WPA/WPA-PSK security. If you want to go wired there is a Gigabit Ethernet port on the back.
The enclosure supports IDE drives. This gives you a chance to use a spare from a previous system upgrade, or go big with a 750GB drive. If even that isn't enough capacity there are 2 USB 2.0 ports that you can attach more drives to.
The DSM-600 is more than a storage device. It has a built in UPnP AV server to stream media to the various computers on your network. You can also use it as an access point to create or supplement a wireless network. Just run the RJ45 cable back to your router and you're all set.