Quite a few, actually. If I had to put my hand on some, here's a list, not necessarily in order of greatness, but all great nevertheless...
- Canning and pickling - while German and Spanish cuisines did some of this before the French and Asian cookery knew about long term storage, often at the expense of taste, French cooking brought canned and pickled foods into haute cuisine and made it palatable.
- Table service - prior to a certain Mr. Boulanger food was essentially served from large pots and pans in the middle of the table. Those foods were prepared offsite and sold to the owners of taverns by the food makers' guild, which, by the way, was not too happy about Mr. Boulanger starting his own kitchen. Boulanger sued, won, and started a trend.
- Frying and Confit - cooking in fats. Without confit and confit accidents, french fries as we know them would not have been as prevalent a side dish that early. The idea of using fat both as a low and slow and hot and fast medium to cook foods isn't French, but French cooks took it to a place from peasant glob to fine dining.
- Front and Back of the House - had it not been for Mr. Escoffier who despaired over the overly French "strutting cock" techniques popularized by Mr. Careme, we'd still be wearing tall hats and medals in the kitchen, standing on plateau shoes, and looking ridiculous while making fancy looking foods that are expensive and make no one except for snobs happy. The modern kitchen and front of the house system is French. Even the American focus on individual tables instead of common tables comes from France.
- Stocks and Sauces - not necessarily invented by the French, but developed and made into a staple by French cooks long before Boulanger started selling them as "magical restoratives" (thus the word "Restaurant") in his shop. Simmering bones to make stock can actually be traced back to have been first documented (I am definitively not believing it was done there first) by the Gauls, proto-Frenchmen if you so will, who stunned the Romans with their cookery. And stunning Romans is hard.
Also great things we kind of owe the French: terroir, cheese making, baking, breads, and wine making.
More questions on French cuisine:
- How is crème fraiche made?
- Cuisine of the Mediterranean coast: What are your favorite places and dishes?
- What is the difference between French and Italian cuisine?