Libox is a cross-platform application that syncs your photos, music and videos across machines, but also lets you stream files from a source computer to any other machine or mobile device you allow.
Libox is basically the combination of Dropbox for your entertainment media (photos/music/videos) and a P2P network. Rather than saving your files online and syncing them to other machines, they just go directly to those other machines. This limits you only by the amount of disk space you have available and allows Libox to remain free. Libox can also act as a streaming server if you don't want to sync your media between machines. If you only install Libox on one machine, you can just access your media remotely through the web browser or via the Libox iOS app. In fact, you don't even really need the iOS app because it's virtually identical to the mobile version of libox.com. Web access also works on Android, and a native application is underway.
If you're an iPhone user and a fan of either Air Video or SteamToMe, Libox isn't really going to replace those apps. For starters, the quality level of streaming video is the same regardless of your connection speeds. This is fine if you're on a slow connection because it streams very well, but if you can handle more data Libox isn't going to adjust for you. Generally the quality is pretty decent, but as you can see in the screenshot above it can get a little overwhelmed if there's a lot going on. Other frustrations include not being able to jump around in the video (this goes for the web client as well as the mobile site/app) and the mobile interface being a little uninformative (as far as locating a specific file goes).
Regardless of any shortcomings, Libox is pretty awesome and it's free. If you need a simple way to stream your media remotely, or just share it between machines and friends, Libox is definitely worth a look.