Hotels in St.Michel district near the RER

This is partially answers your question. The St Michel RER and Metro stations lie along the Blvd St Michel, which is the border between the 5eme and 6eme. The districts are termed arrondissment in French and are numbered working in a circle from the center of the city. The St Michel Metro station is barely in the 6eme. The 5eme and 6eme border the 4eme and the 2eme at the river where the boulevard becomes blvd de Sebastopol. This gives you a choice of districts very close to the RER station. BUT hotels are often identified with areas within or overlapping an arrondissment that take the name of a metro station or geographic landmark. Rick Steves Paris guidebook does this. You can look for hotels in St Germain (pricey) or Contrascarp (less so) Luxembourg, or Ile St Louis and Ile de la Cite (the original Paris settlement in the river) or just over the river. There is a very wide price range so you would do well to check the Steves guidebook or others such as Lonely Planet, Frommers, etc for choices.

Last summer we stayed at Hotel du Lys, which is quite close to the St. Michel RER stop. It is in a very old building, the breakfast is nice but pretty sparse, and the location fantastic.

Hotel Eugenie is 1/2 block away. Clean , good location. Rooms not large or luxe. It is in the 6th, right on border with 5th.
Haven't stayed there, but Hotel Able, seems popular and it is close also( in 5th) .
You could also stay at Hotel Grand Hommes, which is in 5th, but it is near to Luxembourg RER stop, lovely hotel, lovely area.
I also stayed in the 6th at Hotel Le Regent and walked from St Michels RER to our hotel, it was a ten minute walk , but I love Paris, and I pack light, so it is no problem to me.

We stayed at the Hotel Eugenie that Pat mentions and enjoyed staying there. Not especially fancy, not as inexpensive as some, but very clean and safe, and the staff was nice.

We have stayed at the Hotel Eugenie twice and found it to be convenient and a good price for the location. The last time we were there they were remodeling some of the rooms. The rooms are quite small, but you won't be hanging out in the room anyway!! There are several great cafes and bars in the area, Notre Dame is about a 10 min. walk, and, of course, the RER is right around the corner. Enjoy!

in april moms and daughters stayed at the hotel minerve in the latin quarter... the 5th or 6th arrondiss.? I would stay there again. reasonable, clean close to st michael rer ( 4 blocks) pay the extra for room upgrade