There is plenty of street-side shopping since Hong Kong is a very integrated city. Chances are, you will be staying in a tourist area where there are shops everywhere. Tsim Sha Tsui and Causeway Bay are two popular tourist areas where many hotels are.

In fact in Hong Kong, you don't have to go shopping in order to shop. If you have walked on Nathan Road in Tsim Sha Tsui area, you know what I mean. "Copy watch?" you would be asked on the street by people holding a stack of photos of Rolex-look-alikes. If you have a suitcase in tow there, the product offered is tailored to your apparent need. But don't get me wrong, Tsim Sha Tsui is not an area to avoid. Just enjoy the attention and ignore the sales pitch if you don't need the product!

Causeway Bay - for locals living on Hong Kong Island, this is pretty much the "grand central station" when it comes to shopping. Most of the action is concentrated around the MTR station - which has exits going as far as the Times Square. The pedestrain crossing on Yee Wo Street in front of Sogo Department store is often so crowded that the traffic light is not long enough for all to finish crossing the road. With the shortage of street-level stop space, a lot of restaurants have moved upstairs. There are buildings with multiple restaurants on various floors. more

Mongkok - known as the most densely populated area in Hong Kong, it is also one of the most popular shopping areas for locals in Kowloon. The intersection of Nathan Road and Argyle Street is sort of the center of all the action, though things change with times as new shops and malls open. Mongkok Computer Center, Ladies' Market, Sai Yeung Choi Street (with many consumer electronics stores), Nathan Road, and Langham Place (mall and hotel) are some of the hot spots in the area. Meanwhile the goldfish market is the place to pick out some fins. more about Mongkok

• consumer electronics (e.g. cameras, mp3 players, PSP, DiscMan, MiniDisc players, video cameras, multi-system VCR/TV) - Sai Yeung Choi St. South, Mongkok. I would suggest that you check out the prices at the chain stores first.
  

• "Ladies' Market / Women Street": Tung Choi Street, Mongkok. Accessible via MTR. more...
  
• Granville Road, Tsim Sha Tsui (there are many stores selling inexpensive slightly flawed or outlet clothing there - look closely before you leap to the cashier!)
• Wanchai: there are a few stores on Johnston Road right across from the MTR station that sell what seem to be outlet goods. more...
• malls: if you like name brands, malls and shopping centers in Tsim Sha Tsui, Central, Causeway Bay, and Admiralty districts, plus department stores will be the places to go. And then there's the Citygate Outlets shopping center in Tung Chung.
  

• Golden Shopping Arcade - in Sham Shui Po; books, computer supplies, video games and machines in basement and upper ground floor, then the 1st floor has all the computer hardware stores (it seems you must enter this through the outside stairs around the corner). It is just next to the Sham Shui Po MTR station. But beware that the hallways are so crowded with people and the storekeepers' goods that it is downright dangerous in case of any emergency.
  
• Winsor House - in Causeway Bay; close to the Causeway Bay MTR station. It is one of the most pleasant computer centers to look around in with three floors of shops. Unfortunately, at the time of writing, many shops seem to have moved elsewhere.
• 298 Computer Shopping Center - 298 Hennessy Road, Wanchai; between the Wanchai & Causeway Bay MTR stations. Probably easiest to get to by taking a tram going east towards Wanchai from Causeway Bay MTR. It is on the south side of the street close to Heard Street.
  
• Mongkok Computer Center - Mongkok, close to intersection of Nelson St and Tung Choi Street. Close to the Bank Center exit of the Mongkok MTR station. Beware: though smoking is banned in shopping centers, there is still cigarette smoke here.
• Wanchai Computer Center - located next to the Wanchai MTR, it has two floors of shops. It could get a bit crowded though.
• Star House - next to the Star Ferry Pier in TST in Kowloon; some stores not open on Sundays. It is one of the more pleasant computer shopping centers. Unfortunately, the number of stores seems to be in decline. (2008.2)
  
• chain-stores - there are a few chain stores that sell computers and electronic products. Good to check their prices first.

• Ap Liu Street, Sham Shui Po, accessible by MTR. more...

• Hollywood Road - located in Central, this street is known for antique and cool furniture.
• Wong Nai Chung Road - located in Happy Valley next to the horse race track, there are many designer furniture stores.

• chain-stores - there are a few telecom chain stores that sell cell phones and cellular service.
• Ap Liu Street in Sham Shui Po area, accessible by MTR. You can even find second-hand stores there. (It may not be a good place to shop for cell phones if you are gullable.) more...

• Hollywood Road - there are plenty of stores selling antiques there. From spectacles to furniture, you can find them there. But don't expect bargains!
• Cat Street - that's not a pet street, nor can you find feline cuisines there. Actually located on Upper Lascar Row, it's an antiques market with much more old stuff than your grandma's attic. Chairman Mao's badges, old Chinese locks (some posing as such), vases, photos, you name it, they have it in one of the piles.