I use MediaLink which isn't free but works pretty well. It streams flawlessly with my Linksys router. However, I'm just as likely to merely copy video content over to the PS3 HDD. I just feel more comfortable doing it that way rather than having to makeu my Mac is awake.
On note, I used to have a pretty old D-Link router. Streaming with MediaLink was unrelaiable if not impossible with that router.