Ok here is what I found. On your phone, turn on photostream (it appears that once on, any photo you take will end up in the photostream and it creates a second item like your camera roll (photo still shows up in the camera roll too)).
On the PC, in the iCloud control panel, when the photostream is turned on, it creates two folders in your USER\Pictures directory. Uploads and Downloads. Photos then sync from your phone to the PC. You can put photos in the upload folder on your PC in the Photostream directory and they will sync.
I do not see anywhere that you can see the pictures on the Web like we could with Mobile Me.
I think the Apple TV has Photostream on it, but where is it pulling the photos from? Apple TV used to pull them from Mobile Me.