Casanis is a nice, casual french restuarant on Ludlow & Broome. It fairly traditional - both food and decor - and reminds me a lot of the cafes in Paris. Its usually pretty quiet and I've never had to wait for a table.
Les Enfants Terribles on Canal/Ludlow has a great vibe and good African/French fusion. Brown on Hester between Essex/Ludlow is also worth a try, although I've only been for lunch/brunch. Great salads, sandwiches, and their dinner menu has always looked pretty solid.