Istanbul

Accommodation:
Highly recommend the Zeynep Sultan (http://www.zeynepsultanhotel.com/) for 59E/night. Clean and friendly place with fantastic location (Next to Aya Sofia in Sultanahmet), but free wireless access doesn't reach all rooms. Also great is the Hippodrome Hotel (http://www.hippodromehotel.com/) for 65E/night, next to the Blue Mosque in Sultanahmet. Zeynep has slightly better location.
Restaurants & Nightlife:
Reina has a fantastic "Modern Turkish" (Turkish+Mediterranean) menu right on the Bosporus, and turns into a happening (but young) nightclub most nights (particularly Tue/Thu/Fri/Sat). It also hosts a great Chinese restaurant, but both are pricey. Also pricey, on the water at Ortakoy, is Anjelika, with stunning open-air location, decent food, and good crowd (but more of a bar/restaurant, less of a club).

In a similar vein- Sunset has great drinks and view (especially at sunset, surprisingly enough), but Ulus 29 has to take my pick as best food of the upscale bar/lounge/restaurants.

For a more relaxed (and cheaper) traditional Turkish meal, try Hamdi's near the New Mosque. Their flatbreads and kebabs are delicious, and they have a beautiful rooftop deck overlooking the Golden Horn.

Other recommendations I didn't have a chance to try:
360 - restaurant/bar in center of town on the top floor of a residential building with great (360) views of all the key sites. Turns into a little bit of club after dinner.
Leyla/Sortie - huge open air place on the water with a number of restaurants there and a big club on the water (there is a good turkish place there too).
Mangerie - very cute little cafe and restaurant in Bebek (part of town on water with a marina where lots of smaller yachts are moored). Top floor of a building with great views. Good for lunch, coffee or dinner.
Lucca - similar to above. Also in bebek.
Iskele - very good traditional fish restaurant on the water.