I've recently been testing out Windows Home Server Beta. The concept is simple and Home Server is much more than just a NAS device. It adds a bunch of capabilities for keeping various devices (up to 10) on your home network backed up, along with a place to safely keep your network based data on a server.
However, I needed something simple & straightforward that would just plug into the network and give me some safety along with significant space. Along come Hammer Storage myshare
http://www.hammer-storage.com/products/myshare.asp
The version I'm working with is N1200 which gives me 1 Terrabyte of storage total. I have it configured in a mirror set (it has 2 internal 3.5" SATA drives) so, I get 1/2 TB to store my data.
This thing just literally plugs into the network with minor configuration and you're off & running. It supports CIFS (SMB), FTP, NFS, and a simple HTTP browser based view of files that you can also see files, download & upload. Provides ACL based access and setup of users & groups for permissions.
There's also options for attaching external USB devices for backup and printer support. I'm not using the printer support yet.
This device is also extremely quiet. When 1st turning it on, the fan kicks on for about 30 seconds, then it goes nearly silent and is barely noticeable. I have it connected direct to my Router in one of the ethernet ports.
Below are a few shots of the admin screens, but this device is by far the simplest way to get NAS on your home network (business as well) in a simple, secure, and reliable means. It also comes with a 1 year warranty - after a year I'll open up the box and see if I can replace the SATA drives with larger devices - but until then, I don't want to void the warranty. It loads the Linux kernel not from the storage drives, so the drives are upgradeable.