I want to see movies that are on my Mac on the screen connected to my PS3 or Xbox 360
Supposedly works with XBox 360 as well. Supports streaming and transcoding.
I use MediaLink, which lets you use your Mac as a server which the PS3 can connect to for music, pictures, and movies. It seems to work well enough; my only problem is that I don't like the PS3's interface for browsing through large collections of things. For example, when sharing my entire iTunes library, I'm just about restricted to playlists or random shuffle -- pulling a particular artist/album/song out of thousands is just a pain. For movies, it's worked just fine for me.
I use Rivet for streaming to my PS3. It's completely painless to set up, while I've had trouble with another solution in the past (unfortunately I can't remember the name of that one).
I am using Vuze for that: http://www.vuze.com/features/device Not sure if there are any alternatives for OSX.