Mangoes: Bethpage, NY - Mexican joint with some of the most amazing steak fajitas.
Waterzooi: Garden City, NY - Belgian-style bistro, with amazing mussels in a variety of different styles/sauces and pomme frites. Fairly upscale, well at least as far as Long Island is concerned...
Thai Gourmet: South Setauket, NY - The pad ga prow sauce is pretty killer, super spicy too!
Santa-Fe Grill: Hauppauge, NY - Large and filling burritos at an inexpensive price.
Mykonos: Smithtown, NY - Excellent and inexpensive Greek food
House of Dosas: Hicksville, NY - Southern Indian vegetarian cuisine... has some of the spiciest food I've ever had... Dosas are these large crepes with spiced potatoes in the middle, usually served with sambar (spicy vegetable soup) and dipping sauces.
Ancient Ginger: St. James, NY - Some of the best (Americanized) Chinese food I've ever had, without having to go into Queens or Manhattan. Really nice decor, too... definitely kicks the shit out of any takeout place.