Many people have issues streaming media like movies or photos to their PS3 due to the many different networking and security setups which make things complicated. In Windows for example, certain folders are only shared or the network, and if you want to share others you need to change their setting. You try accessing your shared folders on your PS3 and it doesn't let you in anyway due to more security settings you need to change...
Well, I had the same issue up until I found a piece of software called PS3 Media Server.
What an original name!
It's available on Mac, Windows and Linux, and it takes all the fuss out of trying to connect to your hard drives around the home. All you have to do is let it run on the system which has the hard drive you want to share over the network. By default, the entire drive is shared over the network, but this can easily be changed in the settings, and you can select specific folders or drives. Yes, you can plug in an external hard drive, and the software will share it to your PS3. It plays movies over your network with ease, but of course your own experience may differ depending on your network setup. If you're worried about security, it's got plenty of network settings to give you piece of mind.
The thing I love the most though is its huge list of other devices that it supports. Since I discovered that I can stream to my Samsung Smart TV without having to do anything other than have both systems connected to the network, I've been using PS3 Media Server almost on a daily basis. By the way, it also supports XBOX 360!
All you need to do is make sure your PS3 is connected to the same network while the software is running, and in the XMB, the media server should appear (in whichever media type you want to use). Since there is support for so many other devices, I can’t explain how to access network files on every one, but I know for the Samsung Smart TV’s, all you need to do is enter the Sources menu (where you can switch from TV to HDMI etc.) and the media server should appear there.
End the fuss and download it here: http://www.ps3mediaserver.org/
To make it do even more, there's a range of plugins available: http://www.ps3mediaserver.org/forum/viewtopic.php?f=12&t=9078