Enter PlexConnect. The brainchild of Baa, roidy and f00b4r, it’s a super clever little hack which allows a rich, fully-functional Plex client on un-jailbroken ATV2 and ATV3 (1080p!) devices. Essentially, you run a program on your computer which masquerades as the Trailer app. Next, change one setting on the ATV, and you’re up and running. It took me less than 2 minutes to install and get it running. It already uses the new transcoder (which means great support for subtitles), and I suspect it’ll support myPlex soon as well. In the PlexPass preview release of the media server, it also supports AC3 5.1 (remuxing and transcoding from DTS). Another cool thing: it supports iTunes DRM’ed video files.
A really clever hack, especially if you have an Apple TV 3 that so far has no such jailbreak options. Your Mac becomes a DNS server for your Apple TV, fooling it into thinking the content of the Trailers app is coming from Apple when instead it’s coming from an install of Plex.
If you’ve got an Apple TV 2, I highly recommend aTV Flash which lets your Apple TV access network shares and play almost any movie format you can throw at it.