Dining out in Istanbul is a delight. The food tastes great and the table is yours for the evening, while the restaurants hum with activity. Besides this all the traditional Turkish restaurants(meyhane) give the food away. The most popular meyhane are found in Cicek Pasaji(near Taksim Square) where you can expect an inexhaustible variety of appetizers(meze) as well as grilled meat and fish.
Running down the side of Cicek Pasaji is a colourful fish market, with snack stalls selling mussels and kokorec(chopped, fried offal - apparently a must for beating hangovers) and two of the best local eateries; Cumhuryiet and Imroz.
For fish lovers Kumkapi(just behind Sultanahmet) is the place to head for, but be warned it won't be a quiet evening. This site is neatly broken down into different cuisines spanning most of the globe and giving bite-sized reviews of each restaurant. Don't worry about getting there as all taxi drivers(and most locals) have the 'knowledge'.
Frommer's gives impartial and informative reviews of some of the best(and worst) restaurants that Istanbul has to offer; plus a price guide and essential contact information. Frommer's proves an invaluable online resource for the gastronomic traveler.