Muscat City Centre
Muscat City Centre, Seeb, (http://www.citycentremusc...). Currently the biggest mall, containing a lot of shops including a large Carrefour (http://www.carrefouroman.com).
Qurum City Centre
Qurum City Centre.Recently opened up at Qurum and contains Carrefour too (http://www.carrefouroman.com).
Sabco Centre
Sabco Centre, Qurm. Located near the turnoff between Sultan Qaboos St and Qurm Heights Road, the "Sabco Centre" is actually a collection of about half a dozen medium sized shopping centres which is very popular with locals. The actual Sabco Centre has a small souq-like collection of shops that contains many of the handicrafts that are available in the Mutrah Souq. Opposite the Sabco Centre is the Omani Craftsman's House that only sells guaranteed Made in Oman crafts at fixed but relatively high prices.
tailors
There are numerous Indian run tailors. You may pay RO 5 to have 2 Italian suits tailored for sleeve length, trouser length and waist. There is a Raymond store in Ruwi that will make custom suits in the RO 50-60 range. In fact they have excellent fabrics from pure wool to wool blended with exotic fibers like Cashmere, Mohair or Angora and linen. Even Super 230s crafted out of 11.8 micron wool are found there. Ask them for their catalogue - you will find the latest Italian designs and styles in there and a really good suit can be really light on the pocket.