As far as I know there are three networks in HK that provide prepaid SIM data plans, I have got most of the information from the various network's websites, however I have also got additional information from speaking to people, which I have added in here.

Two networks are on 3G/HSDPA and the other is on 2G EDGE.

Networks

Three (3HK)

CSL One2Free

China Mobile (Peoples)

Plan information on websites

3HK HSDPA Broadband Access Rechargeable SIM ("3HK HSDPA")

3HK International Roaming Rechargeable SIM ("3HK IRRS")

3HK Rechargeable SIM ("3HK Rechargeable")

CSL Mobile Data prepaid SIM

Peoples Mobile Data Prepaid SIM Card

Frequency

3HK: 3G/HSDPA 2100 MHz

CSL: 3G/HSDPA 900 & 2100 MHz

Peoples: 2G EDGE 1800 MHz

Where to get the SIM cards

You should be able to pick them up at the airport, but I am not sure of this.

You can definitely pick them up at 3HK, CSL or Peoples stores in HK.

In addition you may be able to pick up the SIM cards from various 7-11's or Circle Ks (but I have not verified this).

3HK also sell their SIM cards at the following locations: ParknShop (supermarket), Fortress (electronics retailer), Watsons (pharmacy), Taste (supermarket) and Citicall (electronics retailer).

For all three companies if you go to the market stalls on Apliu Street, in Sham Shui Po some of them will sell the SIM cards at a discount (around HK$60).

There are no requirements in terms of proof of address, ID, etc. Just pay the cash and you will get the SIM card.

Initial costs & other information

3HK HSDPA
- HK$98 (this counts towards your credit) [Apparently, while the card costs HK$98, it comes with HK$150 credit on it]
- Validity = 180 days from last top up
- Can use the daily data roaming rate
- APN = ipc.three.com.hk

3HK IRRS
- HK$98 (HK$55 stored value with an additional HK$52 of calling credit)
- APN = mobile.three.com.hk

3HK Rechargeable
- HK$198 (this counts towards your credit)
- This is marketed as an Ipad SIM, so it comes with a Micro SIM card. To use with other phones that use the Mini SIM card you need to pick up a Mini SIM card adaptor. These are readily available in Hong Kong and should cost no more than HK$20
- Can use the daily data roaming rate
- APN = imobile.three.com.hk

CSL
- HK$178
- Validity = 60 days from last top up over HK$50
- APN = CSLP2

Peoples
- HK$139 (this counts towards your call credit)
- Validity = 180 days from last top up
- APN = peoples.net

Charges

3HK HSDPA
- Data: HK$2 per MB, capped at HK$28 per day and HK$298 per month
- Full list of charges: http://www.three.com.hk/website/appm...10594&lang=eng
- User guide

3HK IRRS
- Data: HK$2 per MB, capped at HK$28 per day and HK$338 per month
- Full list of charges: http://www.three.com.hk/website/appm...10594&lang=eng
- User guide

3HK Rechargeable
- Data: HK$18 a month, which includes 50MB of data, then HK$2 per MB, capped at HK$28 per day and HK$168 per month
- Wifi: Free Wifi provided by Y5Zone. You do have to register for this service
- Full charges: http://www.three.com.hk/website/appm...10594&lang=eng
- User guide

CSL
- Data: Unlimited = HK$50 1 day pass, HK$178 5 day pass, HK$788 30 day pass
- Full list of charges: http://one2free.hkcsl.com/jsp/prepai...es/charges.jsp

Peoples
- Data: HK$0.04 per KB, unlimited = HK$9 1 day package, HK$38 7 day package, HK$78 30 day package
- Full list of charges: http://www.hk.chinamobile.com/p_prep..._charge_en.jsp

Refill methods (for travellers)

3HK
- Voucher (can be purchased at 7-11's, Circle K, 3HK shops & various other retailers)
- Internet via credit card (note, the recharge website is only compatible with Internet Explorer)
- [There are other refill methods, but these normally are reserved for HK residents]
- More information: http://www.three.com.hk/website/appm...10594&lang=eng

CSL
- Voucher (can be purchased at 7-11's, Circle K, CSL shops & various other retailers)
- Internet via credit card
- [There are other refill methods, but these normally are reserved for HK residents]
- More information: http://one2free.hkcsl.com/jsp/prepai...rge_method.jsp

Peoples
- Voucher (can be purchased at 7-11's, Circle K, Peoples shops & various other retailers)
- Internet via credit card
- [There are other refill methods, but these normally are reserved for HK residents]
- More information: http://www.hk.chinamobile.com/p_prep...sim_vam_en.jsp