Montfermeil and Les Misérables
Montfermeil's main homage to LM consists of the Parc Jean Valjean, which was recently combined with the Parc des Cèdres to form an arboretum, and the nearby Fontaine Jean Valjean.
Whether the Fontaine Jean Valjean actually stands at the spot where Valjean picked up little Cosette's bucket is up for debate: Hugo describes the spring as being in the woods off the road to Chelles, and the fountain's nearest cross street--the chemin de l'Abîme--does indeed lead to Chelles. Nearby street names, such as the Allée du Puits (Alley of the Well) also seem to support this, but the fountain isn't actually that far from the center of town, and I'm not sure whether the area was actually forested in the 19th century. In any case, the fountain and the nearby park make a nice tribute to one of the most iconic scenes of the novel.
The fountain itself can be a bit hard to find, especially since the creation of the arboretum has made most maps of the area inaccurate. To the best of my knowledge, the Place de la Fontaine Jean Valjean is now at the point where the street of the same name meets the new playground built near the arboretum. The fountain is just a niche in the old stone wall there.
No definite location exists for where Hugo intended the Thénardiers' inn to be, but it's probably not a coincidence that he once stayed in a tavern off the Place de la Halle called "Au Rendez-Vous d'Austerlitz."
List of historic places in Montfermeil (French)
La Fontaine Jean Valjean (French)