Impossible is nothing. But hard to do? Yes.
What you’re asking here is; streaming video from your Mac to your PS3.
Simple solution 1:
Why not cut out the Mac, copy the video to an external drive and plug it to your PS3?
The PS3 suports most video formats: MPEG-1, MPEG-2 (PS,TS), H.264/MEPG-4 AVC, MPEG-4 SP. And there are a lot of freeware converters out there.
Simple solution 2:
Get yourself a Apple Mini-DVI-to-video adapter, displays the Mac straight onto your tv.
The hard way
In order for your PS3 to locate files on your mac you would have to set up a netserver. Copy the video files to your server domain (being a certain place on your mac) and locate them trough your PS3 browser.