Lots of shops selling usual tourist fodder as well as local specialities such as Turkish Delight, carpets etc. Most of the branded clothing on offer is fake and is very cheap but the quality can be surprisingly good Check sizes before commiting to buy, especially when buying in markets. Beware of pirate DVDs and games as many will not work despite assurances from vendors.
Real leather can be bought for a good price if you're prepared to haggle. Starting prices are normally at least 2-3 times the final price!
Hairdressing and beauty treatments are good value but beware of tattoo hygiene issues if you decide to be inked permanently.
For food, there is a large supermarket at the end of the main road before the harbour and marina called Tansas which stocks virtually everything including international brands. Tansas has a sister company caled Migros which has two stores in Marmaris, one at the harbour and another larger store on the main road close to the Marmaris Court building. Another hypermarket is situated on the main road beyond the suburb of Armutalan, Kipa is the Turkish divison of Tesco and offers a huge range of international and own brand products at competitive prices.
Most tourists enjoy visiting markets in both Marmaris Armutalan and Icmeler. The markets sell most of the same things the local shops stock but one can haggle a bit more. Beware of pickpockets in these places. The market in the Armutalan area of Marmaris is on a Thursday and the Icmeler market is every Wednesday.
Tortoises: Beware some unscrupulious Turks try to sell baby tortoises to tourists and encourage them to smuggle them back home in luggage as pets. They will die of course in aircraft holds and can be picked up by airport x-ray machines in hand baggage. It is an offence to attempt to import a tortoise into most EU states as they are an endangered species.