In reply to rampantchopper:
Not sure about the camping, but the main tip from me would be plan to get where you want to watch early.... like hours early, if you're watching on a mountain especially the popular areas, then the day before or very early hours and bivi/wild camp near by perhaps. Take lots of food and wine, and enjoy the atmosphere with all the other spectators you get some real characters from all sorts of countries.
I'm not going this year as I'm doing LEJOG while it's on, but when I've seen it previous years, even on mid stage flat areas, the locals all tend to be out with little tables of food a few hours in advance of the race, making it a bit of a street party atmosphere.
I've seen the finish in paris 3 times, and would recomend the corner of the place de la concorde nearest the river as it means you see them come past you, and you see them go back up the champs elysee on the opposite side on each lap. There's also walls and things to perch on to get a better view, and food/drink stands down below on the river - this does require at least 5 hours of keeping your place though!