I just got a Synology 2 bay NAS (the DS213j), and I love it. There is an almost overwhelming amount of things you can do with it.
Another vote for Synology's devices. I had a 110j and it made me very happy, so I upgraded to a 713+ after a couple of years. It's absolutely worth the money. The amount of things I can do with it is astounding:
Time Machine backups.
Personal cloud/FTP/VPN server
Media server, I can access all my media from anywhere particularly great since I don't want to carry my iTunes library on my rMBP due to small SSD. I run Plex and stream video to every device in the house.
Torrent machine
Minecraft server
Web server where I run Apache/MySQL
And it goes on.