No, you need to use Sonys transfer software on your pc to transfer pics, movies or tracks the player can use. You can use the player as a remote storage device though. Some cheap mp3 players function in this way and will play ps3 transfers. The ps3 will work the other way though, allowing you to play/view all your media from your Sony or other mp3 players through it.
Sorry but I have to say Mr. R Moore is wrong. I have a Sony Memory Stick Walkman, and transfers from my PS3 HDD onto memory stick is fine! I have put photos, MP4s and MP3s, game save data etc all onto 17GB USB memory stick via PS3 XMB screen. The PS3 will recognise any external memory device, as long as it has been formated in FAT32. There are only problems when the memory device is too large. Anything above 32GB cannot be formatted to FAT 32. You have to then download a program called Swissknife, to format anything above 32GB!