The Nobel Peace Prize is a highly respected award. I think it will be looked at as a sign by
other nations that Obama respects and values peace and harmony. It could help in the peace process and in conversations with other nations. They may have more respect for his opinions.
The prize itself won't help him in a presidency that already has so much conjecture surrounding it. When he leaves office, and joins the rest of the every day Joes, the prize itself will be forgotten. Once someone is president, that's what people remember them for. The peace prize will mearly be a footnote in a future history text.