Here's what to wear in Paris, the special character and events of each day of the week, maps of Paris, and how to spend your limited time in Paris:

Paris in 1 Day
Take in the panoramic view of the city from the top of the Arc de Triomphe or Tour Montparnasse (much quicker and easier to enter than the Eiffel Tower), then wander down the Champs-Élysées and the rue du Faubourg St-Honoré past the Palais de l'Élysée (home of France's president), the embassy buildings, and the poshest shops in Paris.

Continue along rue Royale to Place de la Concorde and the Jardin des Tuileries, the Louvre, the Seine, Île de la Cité, Notre Dame, then cross to the Left Bank for a look at Place St-Michel and a stroll along the rue St-André-des-Arts in the Latin Quarter. More...

Paris in 2 Days
Spend the first day on the Right Bank following the itinerary outlined above all the way to Place du Chatelet. Start the second day at Notre Dame, climb the Towers, take a look at the Sainte Chapelle and Conciergerie, then explore the Latin Quarter and the Invalides before taking the Métro to Trocadero for the Eiffel Tower. More...

Paris in 3 Days
With three days you can pick several of Paris' excellent museums and spend some time there. I'd recommend the Musée d'Orsay and, depending upon the exhibitions, the Centre Pompidou. You'll also have time for a trip to Sacré Coeur, Montmartre and its lovely views of Paris, and perhaps a historical walking tour. More...

Paris in 4 or 5 Days
With a few more days you can get out of the city on a day-trip excursion, such as to Louis XIV's magnificent Château de Versailles. More...

One Week in Paris
Five days is a sensible time to stay in Paris, and if you have a week or ten days, so much the better. Take a morning or afternoon stroll through Le Marais, historically Paris' Jewish quarter, but today also a lively arts and crafts neighborhood. Spend some time in Paris's lovely parks, and explore some of the medieval monuments such as the Église de St-Germain-des-Prés and the Musée de Cluny. Also, take the easy train ride to Versailles. More...

7 to 10 Days in Paris
Time for more museums, leisurely strolls through the narrow streets of the Île Saint-Louis (and an ice cream cone at Glaces Berthillon), and one or two day-trip excursions from the city to Chartres, Giverny or the châteaux on the Loire. More...

Here's a good place to check tours and prices.

Here are excellent walking tours of Paris.