Please post your favorite links for the DIY trip planner in the comments.
Where to Stay:
Lonely Planet Paris Hotels
20 Paris Hotels Under £100 - This hotel list includes some pretty special places, and while not all are extreme budget picks, they are something to consider.
USA Today Hotel Picks - Our hotel is one of their recommended picks. We like the variety of funky to functional digs.
How to Get Around:
How to use Paris Mass Transportation - A complete guide to using the Paris metro, buses, RER, and tramway.
Metro/RER/bus trip planner - Need to plan your route? This website will tell you how long it will take, what stops will be involved, where you will transfer and how much it will cost on public transportation.
Paris airports website - How to get a shuttle, maps of the 3 terminals and other helpful info.
Paris Velib - The new bike rental system. A very romantic way to get around Paris, with a much better view than the metro.
Planning Your Time: Frommer's online guidebook for Paris - includes itineraries, attraction info, and good walking tour and other maps to paste into your Moleskine.
Other Useful Websites:
Paris Museum Pass - The best deal for museum hoppers is the Paris Museum Pass which can be bought in 2, 4, or 6 day increments. If you're in Paris for the shopping or food, well good for you and God bless your credit card, but if you're here for the art or history, this deal can't be beat. It will get you free admission to most of the sites at a cheaper rate than individual admissions most of the time. We made a list of all the places we want to go, and even with the discount I get for still being under 25, it was cheaper to go with the pass. Another advantage that might sway you, even if you won't save money with the pass, is that you get to skip the ticket lines and go right in at attractions with traditionally long lines, like the Louvre and Versailles.
Paris Walks - A cheap way to upgrade many experiences while traveling is to hire a good guide. The folks at Paris Walks came highly recommended in multiple guidebooks. We'll be going on their Chocolate Walk and discovering why Paris is famous for dark chocolate. This tour is so popular it has to be booked in advance. Shame as the price of the euro to the dollar has become more favorable since we paid. Oh well, I have no regrets.
Fat Tire Bike Tours Paris - Recommended by a pilot friend who always does one of these tours when he has a layover in Paris. We're thinking about booking their Versailles bike tour if it looks like the weather will be good.
The Jules Verne Restaurant has one of the most romantic views in the world, being at the top of the Tour de Eiffel. A bit of a budget buster, you can save a few bucks if you go for a lunch time reservation instead. Reservations required and are better booked months in advance.
Paris Attractions Official Websites: Go to the source for up to date information, dates they are closed, current prices, special exhibits and other useful info.
Tour Eiffel (Eiffel Tower): Champ de Mars, 7th Tel: (01) 4411 2323. Website: http://www.tour-eiffel.fr/ Opening hours: Daily 0930-2300 (Sep-mid Jun); daily 0900-2400 (mid Jun-Aug).
Cathédrale de Notre-Dame (Cathedral of Our Lady): 6 Place du Parvis-Notre-Dame, 4th Tel: (01) 4234 5610 or 4432 1672 (information on tower). Website: http://www.cathedraledeparis.com/ Opening hours: Daily 0745-1845 (cathedral); daily 0930-1845 (towers); Mon-Sat 0930-1130 and 1300-1730 (treasury). Free admission (cathedral); charge for towers and treasury.
La Basilique du Sacré-Coeur (The Sacred Heart Basilica): Parvis du Sacré-Coeur, 18th Tel: (01) 5341 8900.Website: http://www.sacre-coeur-montmartre.com/ Opening hours: Daily 0600-2300 (Basilica); daily 0930-1830 (crypt and dome). Free admission (Basilica); charge for dome and crypt.
Musée National du Louvre (Louvre National Museum): Cour Napoléon, 1st Tel: (01) 4020 5050.Website: http://www.louvre.fr/ Opening hours: daily 0900-1800, Wed and Fri until 2130; closed Tues. Opening hours for temporary exhibitions vary. Admission charge; free first Sun of each month; advance tickets can be purchased from branches of FNAC and on the Internet; tickets allow same-day re-admission.
Musée Rodin (Rodin Museum): 77 rue de Varenne, 7th Tel: (01) 4418 6110. Website: http://www.musee-rodin.fr/ Opening hours: Museum: Tues-Sun 0930-1745, garden: Tues-Sun 0930-1845 (Apr-Sep); museum: Tues-Sun 0930-1645, garden: Tues-Sun 0930-1700 (Oct-Mar). Admission charge; free first Sun of each month.
Musée d'Orsay (Museum of Orsay): Entrances at 1 rue de la Légion d'Honneur and 1 rue de Bellechasse, 7th Tel: (01) 4049 4814. Website: http://www.musee-orsay.fr/ Opening hours: Tues-Sun 0930-1800, Thurs 0930-2145. Admission charge; free first Sun of each month.
Musée du Quai Branly: 17 Quai Branly, 7th Tel: (01) 5661 7000. Website: http://www.quaibranly.fr/ Opening hours: Tue-Sat 1000-1830, Thu open to 2130.
Musée National Picasso (National Picasso Museum): Hôtel Salé, 5 rue de Thorigny, 3rd Tel: (01) 4271 2521. Website: http://www.musee-picasso.fr/ Opening hours: Wed, Fri-Mon 0930-1800, Thurs 0930-2000 (summer); Wed, Fri-Mon 0930-1730, Thurs 0930-2000 (winter). Admission charge; free first Sun of each month.
Centre Georges Pompidou (Georges Pompidou Centre): Place Georges Pompidou, 4th Tel: (01) 4478 1233. Website: http://www.centrepompidou.fr/ Opening hours: Wed-Mon 1100-2100; late-night openings until 2300 for some exhibits. Admission charge; free first Sun of each month.