There should be some kind of automatic selection tool to do the job I would hope. Of course if the subject and background colours are similar it's going to be a nightmare. If you zoom right in and select using lasso, then perhaps you can use a smudge or blur tool to soften the edges, otherwise I'm not sure. Perhaps someone else knows a better way? If you post the picture, I'll have a go in PS for you and let you know how difficult it is and how I did it (if I can!).