I feel like I’m a pretty good home cook, but I would be really interested in a knife skills class or a class about, say, Italian cooking or appetizers or knife skills. Shopping around for classes, so many of them feel either elementary (How to Boil Water) or fluffy. Since they are relatively expensive, I want to make sure I pick wisely.
There are several good cooking schools in NYC that offer programs for amateurs. You can find a great 2-hour knife skills class for under $100, a 3-month immersion course meant for home cooks, and everything in between. Try the Institute for Culinary Education and the New School's Culinary Arts program for a good range of classes. For something a little more professional, try the French Culinary Institute's Amateur Culinary Arts program. For classes focused on healthy/natural cooking, the Natural Gourmet Cookery School has dozens of classes open to the public.
Another route to go is to hire a teacher to come to your home and give you some tips that would be tailored to your needs. Some of these teachers will cook with you and your friends and prepare a dinner to enjoy afterward. Call any of the above-mentioned schools and ask if they have students or graduates who teach privately.