Many fonts on Typekit support French. You can browse fonts that support French by selecting "French" from the list of supported languages in the sidebar under browse fonts.
In order to serve fonts in French, you must enable the "all characters" set in your kit. All fonts that support French include (at minimum) the following letter characters:
| A | B | C | D | E | F | G | H |
| I | J | K | L | M | N | O | P |
| Q | R | S | T | U | V | W | X |
| Y | Z | a | b | c | d | e | f |
| g | h | i | j | k | l | m | n |
| o | p | q | r | s | t | u | v |
| w | x | y | z | Œ | œ | « | » |
| À | Â | Æ | È | É | Ê | Ë |