I have converted my WD MyBook 1 TB hard disk into a network storage device with pogoplug series 4 device. Its available on Amazon.in for about 3500 Rs and turns out cheaper than buying any other network enabled storage device out there in the market. The best part is that you can attach multiple hard disks / pen drives, making it reusable when you buy more storage in future.
Additionally, you can install Arch Linux on pogoplug very easily. Once linux is installed, you can install Samba daemon which let you access all the files through Mac’s finder by mounting the network share.
The maximum file transfer speed I get is around 3 MB per second, which is good enough for HD movies. I combined it with chromecast to watch blue ray movies streamed from it since I am always out of space on my 128GB office Macbook Pro.
I have also install Aria2c, a software which lets you download files through http and torrent protocols on pogoplug device. This helps me schedule a download through the web ui and forget about it. Lets me save power by shutting down my laptop.
The possibilities are endless. You can also install DLNA server on it, which means you can use it to stream media to a DLNA TV. You can also use it as a time machine backup device by installing Netatalk. You can also host your own web server, if your ISP provides a public IP address. All in all, its totally worth the money spent on it. Helps me make full use of my internet bandwidth.