Common words:
* Dans (in, inside)
* De (of, from)
* Deux (two)
* Dire (to say)
* Donner (to give)
* Droit (right, law)
* Dîner (dinner)
* Dimanche (Sunday)
* Dormir (to sleep)
* Déjeuner (lunch)
Less common, but still useful:
* Début (beginning)
* Départ (departure)
* Dépenser (to spend)
* Déjà (already)
* Difficile (difficult)
* Doux (soft, gentle)
* Dame (lady)
* Docteur (doctor)
* Drapeau (flag)
More advanced words:
* Déchirer (to tear)
* Déterminer (to determine)
* Désigner (to designate)
* Développer (to develop)
* Défendre (to defend)
* Diviser (to divide)
* Décrire (to describe)
* Décomposer (to decompose)
Bonus:
* Du (some, any) - This one is actually a contraction of "de" and "le".
This is just a small sample of the many French words that begin with "D"! There are countless others, depending on your level of French and the context you're looking for.