If you've got Windows Media Player 11 you can just use DLNA and your PS3 will see your networked computer and all the shared music, pictures and videos.
Here's the scoop from the PS3 site.
http://manuals.playstation.net/document/en/ps3/current/settings/connectdlna.html
Works great for me. This way you wan't have any software in the way transcoding your files. They'll simply be streamed to your PS3 and played from there. Now if you've got file formats that the PS3 doesn't support then you'll new something like Orb or TVersity or Play On to change the file format on the fly and then stream the result to the PS3. This of course will slow things down a bit so if you can get away with going straight to the PS3 then you should get better performance.
Also, you could upgrade your network to gigabit. That would help performance too. :)
Bryan