Nullriver is now offering its MediaLink application which creates a "seamless solution" for file sharing between the Mac and PS3. A 30-minute free trial is available now, with the full application costing $20.
A quick addendum: DRM'd iTunes music will not play, and Nullriver actually has a good FAQ to check out before going down the media link rabbit hole. We'd love to give an initial report on how well it works, but after getting the Mac and PS3 to recognize each other the concept of "media sharing" failed spectacularly. We'll keep trying, let us know how you fare.