So what can you do once you've turned on ssh support and have command-line access to the box? Plenty. For starters, I quickly mounted shared network drives from my NASes on the network, greatly expanding my storage capabilities.
Under version 1.0, this is a piece of cake because support is in place for Windows shares, AFP shares and NFS shares. But under version 1.1, things get a bit more difficult. As mentioned earlier, native support for Windows network shares is gone, so you'll have to move to external support for Windows network shares. For NFS shares, you can move the mount command back onto the box from another OS X system so that's pretty easy, and you can re-enable AFP support in a similar fashion.
There are a few efforts underway to automatically mount the network shares, but the easiest way to accomplish it is to put your mount commands into a user-created boot-time script called /etc/rc.local.
As for what others are adding to their boxes, the AwkardTV.org web site lists lots of different features. There is information on everything from setting up a remote desktop to setting the box up in a Xgrid compile farm to installing a LAMP stack. All these things are cool, but what I was looking for was a way to extend the video capabilities of the product and that means adding video codecs.
One popular source of OSX-compatible video codecs is Perian. Codecs are provided for a number of different formats including the two most popular: XviD and DivX. If you already had Perian installed on your Mac, and you used the Patchstick creation script, then the codecs were likely installed to your Apple TV as part of the Patchstick boot. If not, then download and install the Perian package on your Mac, then copy the /Library/QuickTime/Perian.component directory to the same location on your Apple TV.
Note that Perian.component is a directory tree, not a single file, so you'll have to do a recursive copy to move it around. When manually adding components to the system directories on your Apple TV, you'll have to go through a couple of steps.
First, the main operating system partition of the drive is mounted read-only. To correct this, from an Apple TV command-line you'll re-mount the OS partition using the command:
# sudo mount -ow /
Sudo Allows non-privileged users, like Frontrow, to issue privileged commands. If you haven't issued the sudo command for a while, it will prompt for the Frontrow user's password (frontrow). Once the drive is mounted read/write, you can copy files wherever you need them (such as the /library/QuickTime/ directory). You'll be prefixing your copy commands with the sudo directive in order to get the right privileges. Once you've finished your modifications, you'll put the OS partition back in read-only mode:
# sudo mount -or /
So now that you've got the codecs installed, you can play your DivX and XviD files right? Wrong. Unfortunately, the Apple TV movie player has already screened out everything except MPEG4 and H.264 files and there's no good way to fix that. The alternative is to move your files over to the ATV yourself, or reference them from a network drive and install an alternate movie player.