These lights may be visited.

Light Location Year(s) of Construction GPS coordinates - Remarks
Les Sept Îles Armor coast 1854, 1952 48° 52' 8"N, 3° 29' 5"W Inhabited and visitable
Trezien Finistére North 1894 48° 25' 27"N, 04° 46' 47"W
Apply to the Office of Tourism in Plouarzel, telephone 02.98.89.69.48.
Roscoff Finistére North 1917 48° 43' 22"N, 03° 58' 50"W
Visitable summer afternoons
Île de Batz Finistére North 1836 48° 44' 46"N, 04° 01' 39"W
Inhabited. Apply to Syndicat d'Initiative de Batz, telephone 02.98.61.75.70 during the summer.
Île Vierge Finistére North 1845, 1902 48° 38' 23"N, 04° 34' 06"W
Inhabited. Visitable during July-August, subject to tidal conditions.
Le Stiff Île d'Ouessant 1695 48° 08' 31"N, 05° 03' 27"W
Visitable during July-August (another source says that it is not open to the public).
Saint Mathieu Finistére, near Brest, Four channel 1740, 1821, 1835 48° 19' 50"N, 04° 46' 18"W
inhabited and visitable
Eckmülh Finistére South, Penmarc'h 1897 47° 47' 900"N, 04° 22' 400"W
Inhabited and visitable
Pen-Men Morbihan 1938 47° 38' 53"N, 03° 30' 034"W
Inhabited and visitable (D. Charles says no).
Goulphar Morbihan, Belle-Île 1836 47° 18' 40"N, 03° 13' 39"W
Inhabited and visitable. There is also a museum here.
Petite Foule Vendee, Île d'Yeu 1829-1831 46° 43' 060"N, 02° 22' 930"W
Inhabited and visitable
Les Baleines Charente Maritime, Île de Ré 1699, 1854 46° 14' 070"N, 01° 33' 070"W
Inhabited and visitable
Chassiron Charente Maritime, Île d'Oléron 1836 46° 02' 9"N, 01° 24' 5"W
Not inhabited, but visitable
La Coubre Charente Maritime 1860, 1895, 1905 45° 41' 8"N, 01° 14' 00"W
Inhabited and visitable
Pointe de Grave Gironde Aux Pyrenees 1827 45° 34' 07"N, 01° 03' 58"W
Check for dates/times.
Museum for Cordouan at this light.
Cap Ferret Gironde 1840 44° 38' 803"N, 01° 14' 85"W
Not inhabited but visitable.
Contis Landes forest 1863 44° 05' 45"N, 01° 19' 10"W
Inhabited and visitable.
Cordouan Gironde 1584 45° 35' 11"N, 01° 10' 25"W
Inhabited and visitable.
Museum: see Pointe de Grave
Cap Camarat Mediterranean 1837 43° 12' 05"N, 06° 40' 50"E
La Garoupe Alps Maritimes 1837 43° 25' 33"N, 06° 52' 19"E
Visitors allowed upon application.
Senetose Corsica 1890 41° 33' 28"N, 08° 47' 55"E
La Chiappa Corsica 1845 41° 35' 40"N, 09° 22' 02"E
Pointe Saint-Martin Pyrénées Atlantiques, Biarritz 1834 43° 29' 6"N, 01° 33' 3"W
Not inhabited but visitable.
La Musée des Phares et Balises Île d'Ouessant   48° 27' 6"N, 5° 07' 8"W
The museum is located at Creac'h. Although you can't visit the light itself, the museum is worth a visit, even if everything is written in French. Bring a dictionary or look at enough French lighthouse websites to get a feel for the vocabulary used.
The source for this information were the books:

Like anything else, things change, and before setting out, it would be prudent to inquire either at the named application point or to the Office of Phares & Balises in Paris.

Bureau des Phares et Balises
3, place Fontenoy
75015 PARIS
Tel: 01.44.49.86.81
Fax: 01.44.49.86.80