The most recent Playstation 3 firmware update (1.80) from Sony not only gave us HDTV owners great new resolution-scaling options, but they slipped in support for media servers as well! I don't run a Media Center PC at home, but found a couple of options for easily setting up a DLNA-compliant media server on my home PC despite the fact.
I've found these two as good options for a PC media server. The first is Microsoft's Windows Media Player 11 and the second is Simplecenter. I went with Simplecenter because I don't have WMP11 installed and after seeing what Simplecenter could do, I definitely thought it was the better option.
Both of these set up guides require that you already have your Playstation 3 connected to your home network as well as your PC. Sony's help for network configuration is here
Using Windows Media Player 11 as the server
Open Windows Media Player 11
From the toolbar, select Library then Media Sharing
Check "Share my media"
On the PS3 - Under Video, Photos or Music, select "Scan for media server"
Go back to the PC, and you should see a pop up showing an unknown device trying to connect.
Allow the device, and everything should work.
Using Simplecenter as the server
Download Simplecenter from http://www.simplecenter.com/
Install - If you only want the basic version, just click next when it asks you to create an account.
Select your shared media folders and let it scan.
Click next one last time.
Check your PS3 and your media server should now be visible.
Other Windows Notes
I've heard that many people are using Nero MediaHome and consider it to be the most feature-rich server
We recently tried setting up my roommate's macbook as a media server using two different products: Allegro Media Server and TwonkyMedia. We had numerous problems with both, including configuration issues, lack of functionality and just general buginess. I've been told that Elgato Eyeconnect works well, but will confirm as soon as I have time.
Comprehensive list of known DLNA-Compliant and UPnP media server applications
Some of these apps are known to handle things like trans-coding and specific X-Box or PS3 features better than others, and since I don't have the time to test them all I'm relying on everyone's comments to help filter out which are the best products. I will try my best to keep this list up-to-date.
Last Updated - 3/23/2009