I've been researching charming, traditional hotels in Paris for a 8-10 day long Paris trip with my sister. I have found quite a few, but would still like to hear if anyone knows about any charming, traditional hotels in the Marais, Ile St-Louis, or St-Germain-de-Pres for under nightly rates of 100 euro. Below are the ones I've scouted out so far:
http://www.paris-hotel-villiers.com/
http://www.paris-hotel-academie.com/
http://www.hotels-paris-opera.com/
http://www.hotelroyalfromentin.com/
http://www.hoteldupantheon.com/
http://www.sully-saint-germain-hotel.com/
http://www.hotelbretonnerie.com/bretonnerie.htm
I think quite a few have summer discounts during the time of our travel, and would gladly appriciate your suggestions.

Other central (eg: Latin Quarter, Opera, Tour Eiffel, etc.) locations in Paris are welcome, but the ones listed above are my personal favorites.

How many of those have air-conditioning? That's something I would require in the summer in Paris, and often becomes the big rejection point for budget Paris hotels.

Think about dividing your stay between two different hotels=two different neighborhoods (i.e. St. Germain/Marais or the Latin Quarter/Eiffel Tour area). We have always done this when we stay at a big city for longer than four nights. The short jaunt between hotels is not that big of a deal. It is fun to get to know two areas of a city a little more intimately as an overnighter. Half our nights this summer will be in the Marais at Hotel Saint Louis Marais and the other half in St. Germain at Hotel Bonaparte. Two years ago, the divide was between Hotel Grand Leveque on Rue Cler and Hotel Minvere near the Sorbonne.

Hotel Jardin de Villiers is just n/e of metro stop Villiers in the 17th. Haven't stayed there but was in this area twice in 1999 - it's a lovely neighborhood with plenty of restaurants, just off rue de Levis market street, Monoprix, walkable to Parc Monceau. It is not, however, in the districts you've specified, nor are the Royal Fromentin (just off blvd Clichy near the sex shops) or Gotty Opera (between metros Cadet and Grands Blvds)...

Are you booking a single room, b/c otherwise I don't think any of these hotels are under 100€ (for a double).