mdt, the official race related stuff is :-
Monday / Tuesday - scrutineering in the city centre
Wednesday pm - 2 x 2 hour qualifying sessions on the circuit
evening onlyThursday pm - 2 x 2 hour qualifying sessions on the circuit
evening onlyFriday - the public road parts of the circuit revert back to public use - so you can 'play' on the track if you like.
Also, the pits are open to the public all day for a 'pit walk'
Late afternoon in the city centre is the grand parade of drivers / majorettes / dancing girls / classic cars etc.
Saturday am - warm up of cars plus support race.
Noon - start / finish area parade / presentation / general jollity (good if you're in a grandstand).
16:00 - they're off - then no sleep til Monday!
Sunday pm - post race piss up / nudity / fireworks etc.
Also around the circuit 'village area' are trade stands, food and beer outlets, t-shirt sellers and the fun fare.
Plus the Le Mans 24 Hour Motor Museum is open all week and worth a couple of hours nose about.
Enjoy - we'll see you there.
see here
http://www.lemans.org/2003/24auto/pages/infos_pratiques_horaires_gb.shtml for 2003's official schedule