I don't know if this is the most effective way but this is what I do.
1)Go to the picture you want and upload it to you XMB, basically on the PS3 main menu go to pictures and it should be there.
2)I put a flash drive in my PS3 and download it onto there.
3)Put the flash drive onto my computer, drag it to my desktop.
4)Go to a upload site, tinypic, photobucket, etc. and upload it there.
If you have trouble just post back and I'll try my best to help you through it.
