lots of tourist accomodation around the train station. Some nicer hotels are near the beach; i.e. Le Meridian. Might be best to make a reservation as the French tend to vacation in August. I think half of Paris will be on the riviera at that time of year!
I too advise you to do so. Nice will be overcrowded along with the French Riviera as the peak of vacation is the first 2 weeks of August. On top, full of foreign tourists. If the Stones do not fill up the stadium, it will be sad, sad, sad. But I am confident.
Use this there are many great hotels in Nice for low prices as well [www.franskehoteller.dk] (the site is in Scandinavian languages and German) hope you find out.
We have a beachparty from stonesplanet.com and RSFCO down below Nellcote the same day.
To book accomodation in Nice, 2 possibilities - you can contact the tourist office and they will tell you what is available at that date and they can probably make the reservation for you (with a small charge) - use an online booking system. I myself always use www.bookings.org, with great offers up to 70 % off. You reserve with a credit card but dont pay until you get to the hotel. You can also cancel up to 24 or 48 hours before you get there.